Call a Cobol program via DB2 stored procedure (Case TS005323974)

A cobol program can be called as routine from another cobol program or via a cobol stored procedure called by a java program

In this second case, the program use a larger number of getpages, on tablespace buffer pool than in the first

The problem is that when a non-result set stored procedure (SP) is called multiple times, DB2 try to keep the internal package structures to be reused for subsequent calls. However, if the SP package calls another package, DB2 doesn't keep the structures of that other package. The reallocation of these structures cause excessive getpages.

Customer environment

We currently having some performance issue when using a call db stored procedure with nested COBOL calls

The current scenario includes two ways to call the nested COBOL module/program:

SCENARIO ONE - COBOL Direct CALL to cobol program:

1. COBOL Program A is running

2. COBOL program A calls COBOL program B, through "CALL MODULE" operation. Program B includes DB2 statements

3. COBOL program B calls COBOL program C, through "CALL MODULE" operation. Program C includes DB2 statements

SCENARIO TWO - COBOL External Stored Procedure CALL to cobol program:

1. JAVA or COBOL Program A is running

2. COBOL program A calls External Stored Procedure (we named it WRAPPER); this pgm does not include any DB2 statement - it acts as a simple wrapper, through a ESP using a DB2 CALL instruction.

3. Stored Procedure Wrapper calls COBOL program B, through "CALL MODULE" operation. Program B includes DB2 statements

4. COBOL program B calls COBOL program C, through "CALL MODULE" operation. Program C includes DB2 statements

This scenario can be applied for batch procedure/processes, while for online transaction everything is managed through Application server.

All programs inside the above scenarios have been compiled adding Interface DSNRLI which allows the ESP calls.

*** Requirement ***

Our Requirement is to have the same performance from Program B and C inside the two scenario as the source code does not change and the called branches/sections remain the same.

*** Issue ***

We noticed that the SCENARIO TWO brings to an increasing of Elapsed and CPU consumption due to getPages operations: every SQL statement is getting more pages if the called program has been invoked through the ESP Wrapper.

Issue has been verified, analyzed and confirmed by IBM lab (TS005323974)

*** Impact ***

The above issue is impacting performance and CPU consumption in:

• Current production procedures [common to all customers that are using the same scenario)

• Future production processes that bring modernization to the current system where communication between current business logic (mainframe) and new Java processes should apply