Stored procedures

A procedure (often called a stored procedure) is a program that can be called to perform operations that can include both host language statements and SQL statements. Procedures in SQL provide the same benefits as procedures in a host language.

DB2^® SQL for iSeries™ stored procedure support provides a way for an SQL application to define and then call a procedure through SQL statements. Stored procedures can be used in both distributed and non-distributed DB2 SQL for iSeries applications. One of the big advantages in using stored procedures is that for distributed applications, the execution of one CALL statement on the application requester, or client, can perform any amount of work on the application server.

You may define a procedure as either an SQL procedure or an external procedure. An external procedure can be any supported high level language program (except System/36* programs and procedures) or a REXX procedure. The procedure does not need to contain SQL statements, but it may contain SQL statements. An SQL procedure is defined entirely in SQL, and can contain SQL statements that include SQL control statements.

Coding stored procedures requires that the user understand the following:

• Stored procedure definition through the CREATE PROCEDURE statement
• Stored procedure invocation through the CALL statement
• Parameter passing conventions
• Methods for returning a completion status to the program invoking the procedure.

You may define stored procedures by using the CREATE PROCEDURE statement. The CREATE PROCEDURE statement adds procedure and parameter definitions to the catalog tables SYSROUTINES and SYSPARMS. These definitions are then accessible by any SQL CALL statement on the system.

To create an external procedure or an SQL procedure, you can use the SQL CREATE PROCEDURE statement.

The following sections describe the SQL statements used to define and call the stored procedure, information about passing parameters to the stored procedure, and examples of stored procedure usage.

For more information about stored procedures, see Stored Procedures, Triggers and User Defined Functions on DB2 Universal Database for iSeries PDF

• Define an external procedure
  The CREATE PROCEDURE statement for an external procedure names the procedure, defines the parameters and their attributes, and gives other information about the procedure that the system uses when it calls the procedure.
• Define an SQL procedure
  The CREATE PROCEDURE statement for SQL procedures names the procedure, defines the parameters and their attributes, provides other information about the procedure that is used when the procedure is called, and defines the procedure body. The procedure body is the executable part of the procedure and is a single SQL statement.
• Invoke a stored procedure
  The SQL CALL statement calls a stored procedure.
• Return result sets from stored procedures
  In addition to returning output parameters, stored procedures have a feature by which a result table associated with a cursor opened in the stored procedure (called a result set) can be returned to the application issuing the CALL statement. That application can then issue fetch requests to read the rows of the result set cursor.
• Parameter passing conventions for stored procedures and UDFs
  The CALL statement and a function call can pass arguments to programs written in all supported host languages and REXX procedures.
• Indicator variables and stored procedures
  Indicator variables can be used with the CALL statement, provided host variables are used for the parameters, to pass additional information to and from the procedure.
• Return a completion status to the calling program
  For SQL procedures, any errors that are not handled in the procedure are returned to the caller in the SQLCA.