Issuing commands from application programs

As with IMS, Db2 commands (including START DB2) can be passed from an APF-authorized program to multiple Db2 subsystems by the MGCRE (SVC 34) z/OS service. Thus, the value of the command prefix identifies the particular subsystem to which the command is directed. The subsystem command prefix is specified, as in IMS, when Db2 is installed (in the SYS1.PARMLIB member IEFSSNxx). Db2 supports the z/OS WTO command and response token (CART) to route individual Db2 command response messages to the invoking application program. Use of the CART is necessary if multiple Db2 commands are issued from a single application program.

For example, to issue DISPLAY THREAD to the default Db2 subsystem from an APF-authorized program that runs as a batch job, use the following code:

MODESUPV DS    0H
         MODESET MODE=SUP,KEY=ZERO
SVC34    SR    0,0
         MGCRE  CMDPARM
         EJECT
CMDPARM  DS    0F
CMDFLG1  DC    X'00'
CMDLENG  DC    AL1(CMDEND-CMDPARM)
CMDFLG2  DC    X'0000'
CMDDATA  DC    C'-DISPLAY THREAD'
CMDEND   DS    0C

Db2 returns the following messages:

DSNV401I - DISPLAY THREAD REPORT FOLLOWS -
DSNV402I - ACTIVE THREADS -
⋮
DSN9022I - DSNVDT '-DISPLAY THREAD' NORMAL COMPLETION

An application program can issue Db2 commands using the instrumentation facility interface (IFI). This method of issuing commands returns information about the success or failure of the command to your program. If the command issues a non-zero return code, the information returned to your program includes diagnostic information about the command processed. For commands that are executed asynchronously, the return code indicates whether the command started successfully.

The IFI application program protocols are available through the IMS, CICS®, TSO attachment facilities, the call attachment facility (CAF), and the Resource Recovery Services attachment facility (RRSAF).