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Oracle Migration Workbench Reference Guide for Informix Dynamic Server 7.3 Migrations
Release 9.2.0 for Microsoft Windows 98/2000 and Microsoft Windows NT
Part Number A97251-01
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3
Triggers, Packages, and Stored Procedures

This chapter includes the following sections:

Introduction

Informix Dynamic Server stores triggers and stored procedures with the server. Oracle stores triggers and stored subprograms with the server. Oracle has three different kinds of stored subprograms: functions, stored procedures, and packages. For detailed discussion on all these objects, see the PL/SQL User's Guide and Reference, Release 1(9.0.1).

Triggers

Triggers provide a way of executing PL/SQL code on the occurrence of specific database events. For example, you can maintain an audit log by setting triggers to fire when insert or update operations are carried out on a table. The insert and update triggers add an entry to an audit table whenever the table is altered.

The actions that Informix Dynamic Server triggers perform are constrained to multiple insert, update, delete, and execute procedure clauses; whereas, Oracle allows triggers to execute arbitrary PL/SQL code. Oracle triggers are similar to stored procedures in that they can contain declarative, execution, and exception handling code blocks.

Additionally, Oracle enables triggers to be invoked by many events other than table insert, update and delete operations. However, there are restrictions.

For more information on trigger restrictions, see the Oracle9i Application Developer's Guide - Fundamentals, Release 1 (9.0.1).

Mapping Triggers

All Informix Dynamic Server trigger types have an equivalent Oracle trigger type. The converter takes the optional WHEN clause in Informix Dynamic Server and converts it to an IF clause. This is shown in the following example:

Informix Dynamic Server SPL

create trigger t_traffic 
update of comments 
on msg_traffic 
referencing new as new 
for each row 
when (new.msg_id>10000) 
 (update msg_traffic set msg_traffic.update_dt = CURRENT year to fraction(3) 
  where (((msg_id = new.msg_id ) AND (msg_source = new.msg_source ) ) 
  AND (sub_msg_id = new.sub_msg_id ) ) );

Oracle PL/SQL

CREATE OR REPLACE TRIGGER t_traffic 
BEFORE UPDATE OF comments ON msg_traffic 
REFERENCING NEW as new_ FOR EACH ROW 
BEGIN 
DECLARE 
ItoO_selcnt         NUMBER; 
ItoO_rowcnt         NUMBER; 
BEGIN 
 IF :new_.msg_id > 10000 THEN 
 UPDATE msg_traffic 
 SET msg_traffic.update_dt  =  SYSDATE 
 WHERE ( ( ( msg_id = :new_.msg_id ) 
 AND ( msg_source = :new_.msg_source ) ) 
 AND ( sub_msg_id = :new_.sub_msg_id ) ); 
 END IF; 
  END; 
END;

Informix Dynamic Server declares triggers on a per table basis with BEFORE and AFTER triggers held together in a single trigger declaration. In Oracle, the BEFORE and AFTER triggers are declared separately. Therefore, the convertor creates multiple Oracle triggers when parsing Informix Dynamic Server per table trigger code.

In the initial release, the Oracle triggers display one after the other in the same text area. The Oracle triggers require manual intervention to build on the Oracle destination database.

Mutating Tables

When you are using Oracle, the trigger or function may cause a mutating table error. This causes you to receive the following error message while executing the trigger:

ORA-04091: table SCOTT.Emp_tab is mutating, trigger/function may not see it.

If you receive this error, you need to manually alter the trigger so that the per row information is stored in an interim PL/SQL table. It is then copied into the destination table after the per row triggers have been fired. For more information, see the Mutating: Containing Tables topic at the following Web site:

http://otn.oracle.com/tech/migration/workbench/htdocs/mutating.htm

Packages

Packages are PL/SQL constructs that enable the grouping of related PL/SQL objects, such as procedures, variables, cursors, functions, constants, and type declarations. Informix Dynamic Server does not support the package construct.

A package can have two parts: a specification and a body. The specification defines a list of all objects that are publicly available to the users of the package. The body defines the code that is used to implement these objects, such as, the code behind the procedures and functions used within the package.

The general PL/SQL syntax for creating a package specification is:

CREATE [OR REPLACE] PACKAGE package_name {IS | AS}
  procedure_specification
..function_specification
..variable_declaration
..type_definition
..exception_declaration
..cursor_declaration
END [package_name];

The general PL/SQL syntax for creating a package body is:

CREATE [OR REPLACE] PACKAGE BODY package_name {IS | AS}
..procedure_definition
..function_definition
..private_variable_declaration
..private_type_definition
..cursor_definition
[BEGIN
  executable_statements
[EXCEPTION
..exception_handlers]]
END [package_name];

The package body is optional. If the package contains only variable, cursor and type definitions then the package body is not required.

As the package specification is accessible to users of the package, it can be used to define global variable definitions within PL/SQL.

The Migration Workbench automatically creates packages during the conversion process for the following reasons:

For more information on package creation, see the following sections:

For more information on package creation and use, see the PL/SQL User's Guide and Reference, Release 1 (9.0.1).

Stored Procedures

Stored procedures provide a powerful way to code application logic that can be stored on the server. Informix Dynamic Server and Oracle both use stored procedures. Oracle also uses an additional type of subprogram called a function.

The language used to code stored procedures is a database-specific procedural extension of SQL. In Oracle it is PL/SQL and in Informix Dynamic Server it is Informix Dynamic Server Stored Procedure Language (SPL). These languages differ considerably. However, most of the individual SQL statements and the procedural constructs, such as if-then-else, are similar in both languages.

Note::

The PL/SQL procedure examples included in the document are the actual output of the Migration Workbench. They are longer than the source Informix Dynamic Server SPL procedures because they are converted to emulate SPL functionality. When the PL/SQL procedures are written for equivalent Oracle functionality, the Output code is shorter.

The PL/SQL procedures, which the Migration Workbench generates, add appropriate comments to indicate the manual conversion required. In general, the Migration Workbench deals with the Informix Dynamic Server constructs in one of the following ways:

The following sections provide a comparison of Informix Dynamic Server and Oracle:

NULL as an Executable Statement

In some cases within stored procedure code, it may be necessary to indicate that no action should be taken. To accomplish this in Oracle, the NULL statement is used. Unlike Informix Dynamic Server, Oracle treats the NULL statement as executable within a PL/SQL code block. In Oracle the NULL statement does not perform an action. Instead, it forms a syntactically legal statement that serves as a placeholder.

Oracle places a NULL statement into PL/SQL code in the following situations:

For information on how the converter uses NULL statements, see the following sections:

Parameter Passing

An Informix Dynamic Server stored procedure contains the following logical parts:

  1. Procedure name

  2. Parameters area

  3. Returning section

  4. Statement block

  5. Document section

  6. With listing directive

Parts two and three define how data is passed to and from a stored procedure. Part two ties data values that are passed by the client to variable names.

Part three is optional. It defines a listing of the data types that the stored procedure returns to the client or calling environment.

The following example demonstrates parts one, two and three: the Informix Dynamic Server stored procedure code for the procedure name, parameters area, and the returning section.

Informix Dynamic Server SPL

/* Procedure name */
CREATE PROCEDURE bal_enquiry( 
/* The Parameters area */
cust_id   NUMBER,
account_num NUMBER) 
/* The Returning section */
RETURNING NUMBER;

Unlike Informix Dynamic Server, Oracle does not require the use of a Returning section. Instead, Oracle passes values to the stored procedure and from the stored procedure by using IN, OUT or IN OUT parameter modes.

In a similar way to Informix Dynamic Server, PL/SQL parameters within Oracle can have default values assigned to them.

Oracle Parameter Passing Modes

The modes for Oracle formal parameters are IN, OUT, or IN OUT. If a mode is not specified for a parameter, it defaults to the IN mode. Table 3-1 describes parameter modes within Oracle.

Table 3-1 Parameter Passing Modes in Oracle
Mode Description

IN

The value of the parameter is passed into the procedure when the procedure is invoked. It is similar to read-only

OUT

Any value the parameter has when it is called is ignored. When the procedure finishes, any value assigned to the parameter during its execution is returned to the calling environment. It is similar to write-only

IN OUT

This mode is a combination of both IN and OUT. The value of the parameter can be passed into the procedure when the procedure is invoked. It is then manipulated within the procedure and returned to the calling environment. It is similar to read-write

Input Parameters

Informix Dynamic Server uses all parameters defined within the parameters area to pass values into the stored procedure. These parameters cannot pass data back to the client. If a default value is included for each variable, clients that execute the procedure do not have to send data to the procedure. Each parameter within the parameters area can, therefore, be converted to a functionally equivalent Oracle IN parameter. An example of an Informix Dynamic Server SPL procedure definition and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

CREATE PROCEDURE informix.update_bal(
cust_id INT,
amount  INT DEFAULT 1)

Oracle PL/SQL

CREATE OR REPLACE PROCEDURE "INFORMIX".update_bal(
cust_id    _IN        NUMBER,
amount_IN         NUMBER DEFAULT 1) AS
BEGIN
cust_id           NUMBER := cust_id_IN;
amount            NUMBER := amount_IN;

Output Parameters

You use the Informix Dynamic Server returning section to define a list of data types to be returned to the client. If you use a returning section, the type and number of data values listed after the RETURN statement must match what was declared in the returning clause. The RETURN statement only sends one set of results back to the calling environment. If multiple contiguous sets of results need to be returned then you can add the WITH RESUME keywords.

If you use the WITH RESUME keywords, after the RETURN statement executes, the next invocation of the procedure starts at the statement that directly follows the RETURN statement.

If a procedure is defined using a WITH RESUME clause, a FOREACH loop within the calling procedure or program must call the procedure. In Informix Dynamic Server, a procedure returning more than one row or set of values is called a cursory procedure.

In effect, Informix Dynamic Server stored procedures have to be invoked repeatedly should multiple values need to be passed back to the calling environment. So n invocations returns n sets of contiguous singleton results.

If the Informix Dynamic Server stored procedure does not contain a WITH RESUME clause, it has been designed to be invoked only once and, optionally, send singleton values back to the calling environment.

In this case, all returning section parameters are converted to be OUT parameters within the generated Oracle PL/SQL code.

If a WITH RESUME statement is present within the Informix Dynamic Server stored procedure, then the Migration Workbench uses each returning clause parameter to build a global temporary table to store the procedures interim results. The Migration Workbench then uses this temporary tableto build and return a populated cursor to the calling environment.

For more information on the strategy the Migration Workbench employs to convert the Informix Dynamic Server returning section to PL/SQL, see the following sections:

Individual SPL Statements

Both Informix Dynamic Server and Oracle use a database-specific procedural extension of SQL as their procedural language. However, the languages are not common so it is necessary that Migration Workbench emulates Informix Dynamic Server functionality that is not found in Oracle within the converted stored procedure PL/SQL code.

The following statements or constructs have to be, to a varying degree of complexity, emulated within the generated Oracle PL/SQL code:

Returning Section

The Informix Dynamic Server returning section is used to define the list of data types being returned to the client. The way the Migration Workbench converts the Returning section is determined by whether the RETURN WITH RESUME statement resides within the Informix Dynamic Server stored procedure. The Migration Workbench converts the returning section using one of the following methods:

Informix Dynamic Server Procedures Containing no WITH RESUME Clause

If only one parameter is specified in the Informix Dynamic Server returning section and the procedure contains no WITH RESUME clause, then Migration Workbench converts the procedure to an Oracle FUNCTION. An example of a procedure returning one value in Informix Dynamic Server and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

CREATE PROCEDURE "informix".add_category(
name like Recipecategory.category_name, 
desc like recipeCategory.category_desc)
RETURNING integer;

Oracle PL/SQL

CREATE OR REPLACE FUNCTION informix.add_category(
  name_IN                Recipecategory.category_name%TYPE,
  desc__IN               recipeCategory.category_desc%TYPE) 
RETURN NUMBER AS

If multiple returning parameters are defined within the Informix Dynamic Server returning section and the procedure contains no WITH RESUME clause, Migration Workbench converts each returning parameter to an Oracle OUT parameter. An example of a procedure returning multiple singleton values and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

CREATE PROCEDURE "root".ocsa_list_total(sp_order_id INT)
    RETURNING DECIMAL(9,4), DECIMAL(9,4),
              DECIMAL(9,4), DECIMAL(10,4);
/* Other statements, one of which is of type
   RETURN <decimal>, <decimal>, <decimal>, <decimal>; */

Oracle PL/SQL

CREATE OR REPLACE PROCEDURE root.ocsa_list_total(
  sp_order_id_IN         NUMBER,
  /* SPCONV-MSG:(RETURNING) Informix RETURNING clause parameters converted to 
Oracle OUT parameters. */
  OMWB_outParameter1  OUT NUMBER,
  OMWB_outParameter2  OUT NUMBER,
  OMWB_outParameter3  OUT NUMBER,
  OMWB_outParameter4  OUT NUMBER) AS
Informix Dynamic Server Procedures Containing a WITH RESUME Clause

The method used to pass sets of results back to the client in Oracle differs considerably from the one used in Informix Dynamic Server.

Oracle stored procedures are only ever invoked once in order to return multiple sets of results and therefore PL/SQL does not contain any such WITH RESUME construct

Multiple sets of data are returned to the calling environment through the use of OUT or IN OUT parameters of type REF CURSOR. This cursor variable is similar to the user-defined record type and array type. The cursor stored in the cursor variable is like any other cursor. It is a reference to a work area associated with a multi-row query. It denotes both the set of rows and a current row in that set. The cursor referred to in the cursor variable can be opened, fetched from, and closed just like any other cursor. Since it is a PL/SQL variable, it can be passed into and out of procedures like any other PL/SQL variable.

If the Informix Dynamic Server stored procedure contains a WITH RESUME clause, the procedure is classed as a cursory procedure, which is a procedure that returns a result set. Each parameter defined within the procedures returning section is then used to construct a global temporary table uniquely associated with the procedure. This global temporary table is then used to store the procedures interim results.

The following Informix Dynamic Server code causes the converter to create a temporary table named get_slistTable. This table is then used to store the interim results of the procedure.

Informix Dynamic Server SPL

CREATE PROCEDURE "root".get_slist(
v_uid like PHPUser.user_id, 
v_listid like ShoppingList.list_id)
returning integer, char(75), char(255);

/* Other stored procedure statements one of which is of type 
   RETURN <integer>, <char>, <char> WITH RESUME                                           
*/

END PROCEDURE;

Oracle PL/SQL temp table Definition

CREATE GLOBAL TEMPORARY TABLE get_slistTable(
/* The first column 'col00' is used to create an ordered
    SELECT statement when populating the REF CURSOR
    OUT parameter to the procedure */
col00  NUMBER,
col01  NUMBER,
col02  CHAR(75),
col03  CHAR(255))
ON COMMIT DELETE ROWS;

The converter then adds an OUT parameter whose type is derived from a packaged WEAK REF CURSOR type to the PL/SQL stored procedure parameter list. For example:

CREATE OR REPLACE PROCEDURE root.get_slist(
  v_uid_IN               informix.PHPUser.user_id%TYPE,
  v_listid_IN            
informix.ShoppingList.list_id%TYPE,
/* The following cursor is added to the procedure by the converter */
  OMWB_ret_cv            OUT
AS

Using a cursor variable in this way in PL/SQL emulates the Informix Dynamic Server cursory procedure. The main difference from Informix Dynamic Server SPL is that the PL/SQL procedure is invoked only once and it returns a cursor variable containing the complete set of results.

For more information, see the following:

DOCUMENT Clause

The DOCUMENT clause enables a synopsis or description of the Informix Dynamic Server stored procedure to be detailed. The text contained after the DOCUMENT keyword is inserted into the Informix Dynamic Server sysprocbody system catalogue during the procedures compilation. This text can then be queried by the users of the stored procedure. Oracle PL/SQL has no such DOCUMENT clause.

The Migration Workbench converts the Informix Dynamic Server DOCUMENT clause to a multi-line comment within the PL/SQL stored procedure. This is demonstrated by the following example:

Informix Dynamic Server SPL

create procedure "informix".min_two(first integer, scd integer) 
returning integer; 
 if (first < scd) then 
  return first; 
 else 
  return scd; 
 end if; 
end procedure 
DOCUMENT 'The following procedure accepts two INTEGER values and returns the 
smallest of the two.';

Oracle PL/SQL

CREATE OR REPLACE FUNCTION informix.min_two( 
 first_IN               NUMBER, 
 scd_IN                 NUMBER) RETURN NUMBER AS 

/* 
'The following procedure accepts two INTEGER values and returns the smallest of 
the two.' 
*/ 

first               NUMBER(10) := first_IN; 
scd                 NUMBER(10) := scd_IN; 
ItoO_selcnt         NUMBER; 
ItoO_rowcnt         NUMBER; 

BEGIN 
 IF ( first < scd ) THEN 
  RETURN first; 
 ELSE 
  RETURN scd; 
 END IF; 
END min_two;

GLOBAL Variable Declarations

Informix Dynamic Server enables the definition of GLOBAL variables by using the GLOBAL keyword within the variable declaration. For example:

Informix Dynamic Server SPL

DEFINE GLOBAL gl_var INT;

This specifies that the GLOBAL variable gl_var is available to other procedures running within the same session. The first declaration of the GLOBAL variable establishes it within the Informix Dynamic Server global environment. Subsequent definitions of the same GLOBAL variable, within other procedures, are ignored.

The first procedure to define the GLOBAL variable can also set its initial value through the use of the DEFAULT clause. For example:

Informix Dynamic Server SPL

DEFINE GLOBAL gl_var INT DEFAULT 20;

If another stored procedure has already defined the GLOBAL variable within the global environment, the DEFAULT clause is ignored.

Therefore, if two procedures define the same GLOBAL variable with different DEFAULT values, the procedure executed first within the current session is the one that sets the GLOBAL variable's initial value.

Informix Dynamic Server GLOBAL variables can be emulated in Oracle by defining the variables within a package.

Variables defined within a package specification are available to the users of the package. The package specification emulates the per-session Informix Dynamic Server global environment.

Two Informix Dynamic Server procedures and the converted equivalent in Oracle are as follows.

Informix Dynamic Server SPL

CREATE PROCEDURE proc01()

      DEFINE GLOBAL gl_var INT DEFAULT 10;
  LET gl_var = gl_var + 1;

END PROCEDURE; 



CREATE PROCEDURE proc02() 

  DEFINE GLOBAL gl_var INT DEFAULT 20;
  LET gl_var = gl_var - 1;

END PROCEDURE;

Oracle PL/SQL Package

CREATE OR REPLACE PACKAGE informix.globalPkg AS
  gl_var  NUMBER;
END globalPkg;

Oracle PL/SQL

CREATE OR REPLACE PROCEDURE informix.proc01 AS
BEGIN
  IF(globalPkg.gl_var IS NULL) THEN
    globalPkg.gl_var := 10; /* Only set default if value is NULL */
  ENDIF;
  globalPkg.gl_var := globalPkg.gl_var +1;
END proc01;

CREATE OR REPLACE PROCEDURE informix.proc02 AS
BEGIN
  IF(globalPkg.gl_var IS NULL) THEN
    globalPkg.gl_var := 20; /* Only set default if value is NULL */
  ENDIF;
  globalPkg.gl_var := globalPkg.gl_var -5;
END proc02;

In the previous example, if proc01 is executed first, the procedure checks if the value of the globalPkg.gl_out packaged variable is NULL. As this is the first time the package has been initialized, the variable contains a NULL value, therefore proc01 sets the value of the globalPkg.gl_var variable to 10 before adding 1 to the value within the statement block. If proc02 is then executed, the procedure again checks to see if the globalPkg.gl_var packaged variable has a NULL value. As proc01 has previously set this variable (initially to 10 and then to 11), the boolean IF statement condition within proc02 IF(globalPkg.gl_var IS NULL) does not return true and the value of 20 is not set. proc02 then subtracts 5 from the current value of the variable, setting its final value to 6.

If proc02 is executed first, it checks if the value of the globalPkg.gl_out variable is NULL. As this is the first time the package has been initialized, the variable contains a NULL value, therefore proc02 sets the value of the globalPkg.gl_out variable to 20 before subtracting 5 from the value within the statement block. If proc01 is then executed, the procedure again checks to see if the globalPkg.gl_out variable has a NULL value. As proc02 has previously set this variable (initially to 20 and then to 15), the boolean IF statement condition IF(INFORMIX.gl_var IS NULL) returns false, therefore, the value of 10 is not set. proc01 then adds 1 to the current value of the variable, setting its final value to 16.

Both the converted procedures reflect the same functionality found within the original Informix Dynamic Server procedures.

LIKE and MATCHES Comparison Conditions

Informix Dynamic Server uses the LIKE and MATCHES comparison conditions to test for matching character strings. Oracle has only one of these pattern-matching constructs, the LIKE clause. The Informix Dynamic Server and Oracle LIKE clauses are functionally identical and so no conversion of the original pattern is required.

The Informix Dynamic Server specific MATCHES clause works in a similar way to the LIKE clause. The only difference between the two types of clause is in the range of pattern-matching wildcard characters available for use. A comparison of the Informix Dynamic Server MATCHES and Oracle LIKE wildcard operators are displayed in tables Table 3-2 and Table 3-3.

Table 3-2 Informix Dynamic Server SPL MATCHES Clause Wildcards
Wildcard Description

*

Matches 0 or more characters

?

Matches any single character.

\

Removes the special significance of the next character used.

[..]

Matches any of the enclosed characters.

^

When used within the [..] wildcard operator, it matches any character not specified within the [..] character range
Table 3-3 Oracle PL/SQL LIKE Clause Wildcards
Wildcard Description

%

Matches 0 or more characters.

_

Matches any single character.

If the [..] pattern matching operator is not used within the original pattern, the Migration Workbench takes one of the following actions when it encounters a MATCHES clause:

If the [..] pattern matching operator is used within the original pattern and a character range is specified, the Migration Workbench converts each MATCHES clause that it encounters to a BETWEEN clause.

If the [..] pattern matching operator is used within the original pattern and no character range has been specified, the Migration Workbench converts each MATCHES clause it encounters to an Oracle IN clause.

The following table presents example Informix Dynamic Server MATCHES clauses and the converted Oracle equivalent:

MATCHES Statements Conversion Results 
MATCHES '[A-Z]    '

BETWEEN 'A' AND 'Z'

MATCHES '[abcdefg]'   '

IN ('a','b','c','d','e','f','g')

MATCHES '*tennis* '

LIKE '%tennis%'

MATCHES '?ennifer*    '

LIKE '_ennifer%'

MATCHES '[^qwerty]    '

NOT IN ('q','w','e','r','t','y')

MATCHES '[^a-z]   

NOT BETWEEN 'a' AND 'z'

If the Migration Workbench can not fully convert an Informix Dynamic Server MATCHES clause, it takes the following actions:

  1. Generates a warning within the converted PL/SQL stored procedure code.

  2. Converts the Informix Dynamic Server MATCHES keyword to the PL/SQL LIKE keyword.

  3. The original pattern remains unchanged.

It is therefore necessary for you to manually convert any search pattern not handled by the Migration Workbench.

FOR LOOP Constructs

Informix Dynamic Server allows a number of FOR LOOP constructs that Oracle does not support. The most difficult of these to convert to Oracle is a FOR LOOP that mixes RANGE and EXPRESSION LISTs within the same iteration definition. In PL/SQL, it is necessary to split each defined iteration range into its own unique FOR LOOP or functionally equivalent PL/SQL code block.

In the following example, the converter splits the original Informix Dynamic Server FOR LOOP construct into four functionally equivalent PL/SQL code blocks. One PL/SQL code block for each iteration range defined within the Informix Dynamic Server FOR LOOP construct. An example of an Informix Dynamic Server FOR LOOP construct and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

CREATE PROCEDURE forloop_example()

  DEFINE iterator_var, j INT;
  LET j = 10;
  FOR iterator_var IN (

      /* A range definition */
      1 TO 20 STEP 2,
      /* a SELECT statement */
      (SELECT aval from atable where avalid = j),
      /* An expression range definition */
      j+10 TO j-20,
      /* A singleton value */
      1000)
          INSERT INTO testtable VALUES(iterator_var);

  END FOR;

END PROCEDURE;

Oracle PL/SQL

CREATE OR REPLACE PROCEDURE forloop_example AS
iterator_var        NUMBER(10);
j                   NUMBER(10);
ItoO_selcnt         NUMBER;
ItoO_rowcnt         NUMBER;

CURSOR cursor1 IS 

  SELECT aval 
  FROM atable 
  WHERE avalid = j;

BEGIN 

  j := 10; 
/* A range definition */
  iterator_var := 1;

 LOOP 

      INSERT INTO testtable 
      VALUES(iterator_var);
      iterator_var := iterator_var + 2;
      EXIT WHEN (iterator_var >= 20);

 END LOOP;
/* A SELECT statement */
FOR cursor1Record IN cursor1 LOOP 

      iterator_var := cursor1Record.aval;
      INSERT INTO testtable 
      VALUES(iterator_var);

 END LOOP;
/* An expression range definition */
FOR iterator_var IN j + 10 .. j - 20 LOOP 

      INSERT INTO testtable 
      VALUES(iterator_var);

 END LOOP;
/* A singleton value */
iterator_var := 1000;
INSERT INTO testtable
 VALUES(iterator_var);
END forloop_example;

FOREACH LOOP Constructs

An Informix Dynamic Server FOREACH LOOP is the equivalent of a PL/SQL cursor. When an Informix Dynamic Server FOREACH statement executes, the database server:

  1. Declares and implicitly opens a cursor.

  2. Obtains the first row from the query contained within the FOREACH LOOP or it obtains the first set of values returned by the procedure.

  3. Assigns each variable in the variable list the value of the corresponding value from the active set that the SELECT statement or called cursory procedure returns.

  4. Executes the statement block.

  5. Fetches the next row from the SELECT statement or procedure on each iteration and repeats steps 3, 4, and 5.

  6. Terminates the loop when it finds no more rows that satisfy the SELECT statement or when no more data is returned from the procedure. The implicit cursor is closed when the loop terminates.

Within Informix Dynamic Server, FOREACH statements can be one of following types:

FOREACH .. SELECT .. INTO Statement

The Migration Workbench emulates FOREACH .. SELECT .. INTO statement in PL/SQL by converting the Informix Dynamic Server FOR EACH SELECT statement into a cursor definition. Then it iterates over the cursor contents, assigning the values within the current cursor row to the original list of variables defined within the SELECT INTO statement. Migration Workbench repeats this process until no more data is found. An example of a FOREACH..SELECT..INTO statement and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

DECLARE name VARCHAR(30);
DECLARE address VARCHAR(255);
FOREACH SELECT ename, eaddress INTO name, address FROM emp
  INSERT INTO mailing_list VALUES(name, address);
END FOREACH;

Oracle PL/SQL

/* Declare original variables */
name VARCHAR(30);
address VARCHAR(255);

/* Declare a cursor using the original SELECT statement 
   Notice how the converter has now named the cursor within 
   PL/SQL */
CURSOR cursor1 IS
  SELECT ename, eaddress
  FROM emp;
BEGIN
  /* Open the previously declared (now) named cursor */
  OPEN cursor1;
  /* Iterate over the cursor contents */
  LOOP

      /* Fetch the values of the cursor's current row 
     into the original variables */
      FETCH cursor1
      INTO name, 
     address;
      /* Exit the LOOP when no more data found */
      EXIT WHEN cursor1%NOTFOUND;
      /* The original statement block */
      INSERT INTO mailing_list 
VALUES(name, 
       address);

 END LOOP;
 /* Close the cursor */
 CLOSE cursor1;
END;
FOREACH CURSOR Statement

An Informix Dynamic Server FOREACH statement can contain an explicitly named cursor. This enables the use of the WHERE CURRENT OF clause within the statement block contained within the FOREACH construct. The Informix Dynamic Server FOREACH cursor statement is converted to PL/SQL in a similar way to the FOREACH.. SELECT .. INTO statement. The named cursor is defined within the PL/SQL procedure, opened, and the contents iterated over until no more data is found. A FOREACH CURSOR statement and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

CREATE PROCEDURE "informix".update_list
DECLARE name VARCHAR(30);
DECLARE address VARCHAR(255);
FOREACH namedCursor FOR
  SELECT ename, eaddress INTO name, address FROM emp
  INSERT INTO mailing_list VALUES(name, address);
  IF(ename="McAllister") THEN
    UPDATE emp SET sal = sal + 2000 WHERE CURRENT OF namedCursor;
    CONTINUE FOREACH;
  END IF
  UPDATE emp SET sal = sal + 1000 WHERE CURRENT OF namedCursor;
END FOREACH
END PROCEDURE

Oracle PL/SQL

CREATE OR REPLACE PROCEDURE "informix".update_list AS

name                VARCHAR2(30);
address             VARCHAR2(255);
ItoO_selcnt         NUMBER;
ItoO_rowcnt         NUMBER;

CURSOR namedCursor IS 

  SELECT ename,
         eaddress 
  FROM emp FOR UPDATE;

BEGIN 

OPEN namedCursor;
LOOP

      FETCH namedCursor 
INTO name,

address;

EXIT WHEN namedCursor%NOTFOUND;
INSERT INTO mailing_list 
VALUES(name,
       address); 
  IF ( ename = 'McAllister' ) THEN

          UPDATE emp 

                  SET sal  =  sal + 2000 
              WHERE CURRENT OF namedCursor; 
              /* SPCONV-MSG:(CONTINUE FOREACH) Statement emulated using GOTO     
       statement and LABEL definition. */
              GOTO Continue_ForEach1;

          END IF; 
      UPDATE emp 
      SET sal  =  sal + 1000 
      WHERE CURRENT OF namedCursor;
      <<Continue_ForEach1>>
      NULL;

 END LOOP;
 CLOSE namedCursor;
END update_list;

For more information on the translation of Informix Dynamic Server CONTINUE statements, see Converting CONTINUE Statements.

FOREACH Execute Procedure Statement

If a FOREACH execute statement is encountered by the convertor, it assumes the procedure being called is a cursory procedure. As cursory procedures are automatically converted to utilize PL/SQL REF CURSORS, the procedure being called always return a REF CURSOR as it's last parameter. This cursor variable contains the full set of results returned by the called stored procedures.

The Informix Dynamic Server FOREACH EXECUTE statement can be emulated by iterating over the contents of the cursor variable returned by the converted cursory procedure.

The following shows an example of the Informix Dynamic Server FOREACH EXECUTE statement repeatedly executing a cursory procedure bar() until no more results are returned and the converted equivalent in Oracle:

Informix Dynamic Server SPL

FOREACH EXECUTE PROCEDURE bar(100,200) INTO i
  INSERT INTO tab2 VALUES(i);
END FOREACH

Oracle PL/SQL

/* DEFINE a cursor variable of the correct type */
OMWB_cv1 OMWB_emulation.globalPkg.RCT1;

/* Cursor variable added to the call to procedure bar() */
bar(100,200,OMWB_cv1); 
/* Iterate over the cursor contents */
LOOP
  /* FETCH the contents into the original variable */
  FETCH OMWB_cv1 
  INTO i;
  /* EXIT the LOOP when no more data found */
  EXIT WHEN OMWB_cv1%NOTFOUND;
  /* execute statement block */
  INSERT INTO tab2 VALUES(i);
END LOOP;

Compound LET Statements

Informix Dynamic Server uses the LET statement to assign values to variables. PL/SQL only allows simple assignments, which assign a single value to a single variable. Informix Dynamic Server SPL allows compound assignments, which assign values to two or more variables within the same statement.

In order to convert compound LET statements into functionally equivalent PL/SQL code, the converter splits the Informix Dynamic Server compound assignment statement into logically equivalent simple assignment statements.

An example of both Informix Dynamic Server simple assignments and compound assignments and the converted equivalent in Oracle are as follows:

Informix Dynamic Server SPL

/* Simple assignment */
LET a = 10;               
/* Compound assignment */
LET b,c = 20,30;

Oracle PL/SQL

/* Simple assignment conversion*/
a := 10;
/* Compound assignment conversion*/
b := 20;
c := 30;

The two original Informix Dynamic Server LET statements have been converted into three logically equivalent PL/SQL statements. One PL/SQL statement for every variable used within both Informix Dynamic Server LET statements. Informix Dynamic Server also enables SELECT statements and PROCEDURE calls to assign values to variables within a LET statement.

Using SELECT Statements in LET Assignment Statements

Informix Dynamic Server enables the use of a SELECT statement as part of the LET statement assignment list.

The following shows an example of an Informix Dynamic Server SELECT statement as part of a LET statement assignment list and the converted equivalent in PL/SQL:

Informix Dynamic Server SPL

LET enum = (SELECT empnum FROM emp WHERE empname = "McAllister");

Oracle PL/SQL

SELECT empnum INTO enum FROM emp WHERE empname = 'McAllister';
Calling Procedures in LET Assignment Statements

Informix Dynamic Server enables the use of a procedure call within a LET statement. The procedure may return more than one value into a list of variables.

An example of an Informix Dynamic Server procedure call that returns three values into the variables a, b, and c and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

LET a,b,c = someProc(100,200);

Oracle PL/SQL

someProc(100, 200, OMWB_outparameter1 => a, OMWB_outparameter2 => b, OMWB_
outparameter3 => c);

The someProc procedure is converted to pass these values back as Oracle OUT parameters. These OUT parameters are explicitly named:

OMWB_outparamater<number>

Thus, if the original Informix Dynamic Server stored procedure returned n values, the converter adds n OUT parameters to the converted stored procedure, sequentially named OMWB_outparameter1 .. OMWB_outparametern.

An example of an Informix Dynamic Server LET statement which assigns a value to only one variable and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

LET a = anotherProc(200);

In the above example, the converter assumes that the procedure being called has been converted to a function within PL/SQL and convert the statement to read:

Oracle PL/SQL

a := anotherProc(200);

For more information on named and positional parameter passing notation, see the following:

Converting CONTINUE Statements

An Informix Dynamic Server CONTINUE statement is used to start the next iteration of the innermost FOR, FOREACH or WHILE loop. When a CONTINUE statement is encountered, the rest of the statements contained within the innermost LOOP of the innermost TYPE are skipped and execution continues at the next iteration of the LOOP.

Oracle PL/SQL does not contain a CONTINUE statement so Migration Workbench emulates the statement by using a PL/SQL LABEL definition and a code branching GOTO statement. This label is defined as the penultimate statement within the converted looping constructs statement block. As PL/SQL requires the statement directly following a label definition to be executable, Migration Workbench adds a NULL statement directly after the inserted label definition. The END LOOP PL/SQL statement is declarative, not executable, whereas, the NULL statement within PL/SQL is executable.

An example of an Informix Dynamic Server CONTINUE statement and its converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

CREATE PROCEDURE continue_test()
indx  INT;
FOR indx IN 1 TO 10 LOOP
  IF(indx = 5) THEN 
    CONTINUE FOR;
  END IF
  INSERT INTO tab VALUES(indx) ;
END FOR

Oracle PL/SQL

CREATE OR REPLACE PROCEDURE continue_test AS
indx INTEGER;
BEGIN
  FOR indx IN 1 .. 10 LOOP
    IF(indx = 5) THEN 
      /* The original Informix CONTINUE statement has been 
          replaced by a PL/SQL GOTO statement*/
      GOTO FOR_LABEL1;
    END IF
    /* Original statement block */
    INSERT INTO tab VALUES(indx) ;
    /* The following label definition are placed at the end of the 
        LOOP constructs statement block*/
    <<FOR_LABEL1>>
    /* Label definitions have to be followed by an executable
       statement. As PL/SQL treats the END LOOP statement as
       being declarative, a NULL statement is placed after
       the label definition. NULL statements within PL/SQL are 
       classed as being executable */ 
    NULL;
  END LOOP;
END;

Converting RETURN WITH RESUME Statements

Informix Dynamic Server enables procedures to return multiple sets of results by the inclusion of the WITH RESUME keywords after the RETURN statement. An Informix Dynamic Server procedure of this type is called a cursory procedure.

The result set returned by an Informix Dynamic Server cursory procedure is emulated within Oracle by adding a REF CURSOR variable to the parameter list of the converted PL/SQL procedure.

This cursor variable stores the complete set of results returned from the stored procedure.

An Oracle temporary table is used to return an identical set of results in an identical order within the PL/SQL procedure as would have been returned in the original Informix Dynamic Server procedure. This temporary table stores the interim results in an ordered sequence.

In the following Informix Dynamic Server example, the procedure returns every continuous integer value between 1 and 100, except the values between 49 and 61, in ascending order to the parent procedure or calling environment.

In order to successfully emulate the order in which these results are returned in Informix Dynamic Server, the Migration Workbench creates a GLOBAL TEMPORARY TABLE specifically to store the interim procedure results. The Migration Workbench then converts the Informix Dynamic Server RETURN WITH RESUME statement to INSERT results into this temporary table. The Migration Workbench then uses the temporary table to populate the cursor returned to the calling environment.

An example of a RETURN WITH RESUME statement and the converted equivalent in Oracle is as follows:

Informix Dynamic Server SPL

CREATE PROCEDURE resume_test() RETURNING NUMBER;
indx INT;
FOR indx = 1 to 100 LOOP
  IF(indx > 49 and indx < 61) THEN
    CONTINUE FOR;
  END IF
  RETURN indx WITH RESUME;
END FOR;
END resume_test;

Oracle PL/SQL temporary table DDL statement

CREATE GLOBAL TEMPORARY TABLE resume_testTable(
/* The first column 'col00' is used to create an ordered 
    SELECT statement when populating the REF CURSOR
    OUT parameter to the procedure */
col00  NUMBER,
col01  NUMBER)
ON COMMIT DELETE ROWS;

Oracle PL/SQL Converted Procedure

CREATE OR REPLACE PROCEDURE resume_test(
/* Define the cursor used to pass back the complete list
   of results to the calling environment as an OUT    
   parameter  */
OMWB_ret_cv OUT OMWB_emulation.globalPkg.RCT1)
AS
indx INTEGER;
/* A counter is automatically added by the converter.    
   This is used to INSERT a sequential set of results 
   into the GLOBAL TEMPORARY TABLE resume_testTable. */ 
OMWB_resume_testSeq INTEGER := 0;
BEGIN
/* Clear the temporary table of old results at the start    
   of the procedure */
DELETE FROM resume_testTable;
FOR indx IN 1 .. 100 LOOP
  IF(indx > 49 and indx < 61) THEN
    /* CONTINUE statement emulated by using a GOTO
       statement and LABEL definition */
    GOTO FOR_LABEL1;
  END IF;
  /* Return with resume statement converted to INSERT the
     return data into this procedures GLOBAL TEMPORARY 
     TABLE. 
     The OMWB_resume_testSeq variable is used in order to 
     create a continuous sequence of values when ordering 
     the results for insertion into the return cursor 
     OMWB_ret_cv */
  INSERT INTO resume_testTable
  VALUES(OMWB_resume_testSeq,
         indx);
  /* Now we increment the sequence variable ready for the 
     next converted RETURN WITH RESUME statement */
  OMWB_resume_testSeq := OMWB_resume_testSeq + 1;
  /* Label definition used by the GOTO statement above */
  <<FOR_LABEL1>>
  NULL;
END LOOP;
/* The temporary table is then used to populate the 
   REF CURSOR we return to the calling environment. 
   The first column is used to return the results from 
   the select statement in an ordered fashion and is 
   never made part of the return data */
  OPEN OMWB_ret_cv FOR
  SELECT col01
  FROM resume_testTable
  ORDER BY col00;
END resume_test;

When the PL/SQL procedure in this example is called, it deletes past results from the associated temporary table of the procedure using the DELETE FROM syntax. For example:

Oracle PL/SQL

DELETE FROM resume_testTable;

The table is now void of results and ready for use within the procedure. The Informix Dynamic Server RETURN WITH RESUME statement is then converted to INSERT results into this temporary table. An INTEGER variable called:

OMWB_<procedure name>Seq

This is automatically added to the variable declaration section within the stored procedure. This variable is used to insert an ordered sequence number into the first column of the resume_testTable table.

To populate the cursor variable designed to return the results to the calling environment, the converter then adds an OPEN CURSOR .. FOR .. SELECT statement as the last executable line of the procedure. At this stage of the procedures execution, the temporary table is populated with a full set of results.

The first column of the temporary table is used within the ORDER BY section of the last SELECT statement to populate the cursor rows with the ordered temporary table data. The procedure completes execution and the populated cursor is returned to the calling environment.

Built-in Functions

Some built-in functions within Informix Dynamic Server are not available in Oracle. These functions are emulated within Oracle using the utilities package. Migration Workbench automatically creates this package within the destination Oracle database. It contains a suite of PL/SQL stored functions and procedures that mimic the functionality of the following Informix Dynamic Server built-in procedures:

The Migration Workbench creates a new user within the destination Oracle database. The user name is OMWB_emulation and the password is oracle. This OMWB_emulation users schema stores the utilities package. To enable access to this package to all database users, the Migration Workbench executes the following statement:

Oracle PL/SQL

GRANT EXECUTE ON OMWB_emulation.utilities TO PUBLIC;

Every time the stored procedure converter encounters a reference to one of the unsupported built-in functions within the Informix Dynamic Server SPL code, it generates a reference to the equivalent emulation function within the OMWB_emulation users utilities package. An example of a SPL statement converted to reference the OMWB_emulation.utilities.HEX emulation function within Oracle is as follows:

Informix Dynamic Server SPL

LET a = HEX(255);

Oracle PL/SQL

a := OMWB_emulation.utilities.HEX(255);

With the exception of the Informix Dynamic Server TRACE function, all emulation functions have the same names as their Informix Dynamic Server counterpart. The TRACE statement is converted to reference a procedure named DEBUG within the OMWB_emulation.utilities package.

Caution:

It is imperative that you test the utilities package and all functions and procedures within before implementation in a production environment.

Converting the SYSTEM Statement

The SYSTEM statement enables operating system commands to be executed from within an Informix Dynamic Server stored procedure. For example:

Informix Dynamic Server SPL

SYSTEM ` ls -al /tmp/salary_upgrades > /tmp/salary_upgrades/totals.out';

Oracle does not have any such SYSTEM statement so it is necessary to emulate the Informix Dynamic Server SYSTEM functionality by using an Oracle external procedure. This external procedure is written in C and compiled into an executable. A stored procedure named SHELL is then associated with a call to the executable.

In essence, a call to the associated PL/SQL stored procedure actually invokes the compiled executable resident on the file system. This binary executable then performs the operating system command passed into the SHELL stored procedure. You need to manually compile this executable before emulation of the Informix Dynamic Server SYSTEM command can commence.

The Migration Workbench creates a placeholder PL/SQL stored procedure named SHELL within the OMWB_Emulation users schema. It then converts each Informix Dynamic Server SYSTEM statement to reference this placeholder procedure. For example, the previous SYSTEM statement is converted into the following PL/SQL code:

Oracle PL/SQL

OMWB_Emulation.SHELL(` ls -al /tmp/salary_upgrades >
/tmp/salary_upgrades/totals.out');

This placeholder procedure currently contains no executable code, it is a stub created within the destination database so that any procedure containing references to it does not fail compilation.

Oracle invalidates a stored procedure if any other stored procedure it references is itself invalid. Therefore, the stub procedure is required until the set-up tasks have been performed. If the stub procedure is invoked prior to the set-up tasks being performed, the string containing the operating system command is not executed.

Set-Up Tasks for Configuring the SHELL Procedure In order to configure the SHELL procedure so that it executes the operating system command, you should first perform the following set-up tasks on the destination server:

Note::

The following set-up tasks are specific to Windows NT.
  1. Download and install Borland's free C++ compiler from the Web site at:

http://www.borland.com

  1. Create the file shell.c:

       ==============begin shell.c=================
   #include <windows.h>
   #include <stdio.h>
   #include <stdlib.h>

   void __declspec(dllexport) sh(char *);
   void sh(char *cmd)
   {
   system(cmd);
   }

   ============end shell.c======================
  2. Create a test program shell_run.c:

       =============begin shell_run.c===============

   void __declspec(dllimport)ch (char*);

   int main(int argc, char *argv[])
   {
   sh(argv[1]);
   return 0;
   }

   ============end shell_run.c==================
  3. Create and run shell_compile.bat that compiles and link shell.c and shell_run_c:

       ============begin shell_compile.bat =========

   bcc32 -WD shell.c
   implib shell.lib shell.dll
   bcc32 shell_run.c shell.lib

   ============end shell_compile.bat ===========
  4. Test shell.dll by issuing the following command on the DOS prompt:

     C:\> shell_run "any operating system command"
  5. Configure the destination databases listener.ora and tnsnames.ora files for external procedures.

For the configuration of external procedures, you need to define a tnsnames.ora entry: extproc_connection_data.

When the server references an external-procedure, it looks into the tnsnames.ora file to find the listener address. The alias used is the hard-coded extproc_connection_data value. This alias contains the address of the listener process and the SID for the extproc agent. With this info, the server contacts the listener and the listener spawns the new extproc-process.

Add the following entry to the tnsnames.ora file:

 EXTPROC_CONNECTION_DATA =
   (DESCRIPTION =
     (ADDRESS_LIST =
       (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))
     )
     (CONNECT_DATA =
       (SID = PLSExtProc_817)
       (PRESENTATION = RO)
     )
   )

Configure the listener.ora file, add an SID_DESC entry similar to the

following:

 SID_LIST_LISTENER =
   (SID_LIST =
     (SID_DESC =
       (SID_NAME = PLSExtProc_817)
       (ORACLE_HOME = <ORACLE_HOME>)
       (PROGRAM = extproc)
     )
    )
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