08/12/08 Creating a single startup program for multiple systems

This tip is particularly useful if you are using an iSeries high availability product for disaster recovery purposes. The idea is to create one startup program that will work on two or more systems -- one source code for multiple systems.

Use a data area to define the system's role in the iSeries replication environment. For example, the production system data area would have a setting of SRC and the backup system the setting of TGT. You may also want to define a value of SWT when the system is in the process of switching.

When a system is the production system, you want production subsystems/processes to start when the system is IPL'd. When a system is the backup system, you likely do not want these subsystems/processes to be started when the backup system is IPL'd. Of course, there will be some things you will want to start on all systems regardless of its role.

In the startup program, retrieve the pre-defined data area and then process accordingly.

Example source code for the startup program:


PGM
DCL VAR(&SYSROLE) TYPE(*CHAR) LEN(3)
RTVDTAARA DTAARA(YOURLIB/SYSROLE (1 3)) RTNVAR(&RTNVAL)
MONMSG MSGID(CPF1015) EXEC(CHGVAR VAR(&RTNVAL) +
VALUE('UNK'))

SELECT
WHEN COND(&SYSROLE = 'SRC') THEN(DO)

/* INSERT COMMANDS TO RUN WHEN SYSTEM IS THE SOURCE */

ENDDO

WHEN COND(&SYSROLE = 'TGT') THEN(DO)

/* INSERT COMMANDS TO RUN WHEN SYSTEM IS THE TARGET */

ENDDO

WHEN COND(&SYSROLE = 'SWT') THEN(DO)

/* INSERT COMMANDS TO RUN WHEN SYSTEM IS MID SWITCH */

ENDDO
ENDSELECT

/* INSERT COMMANDS TO RUN REGARDLESS OF SYSTEM ROLE */

ENDPGM



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