Before a CICS application can issue any DL/I calls, it must indicate to IMS its intent to use a particular PSB by using method schedulePsb: in class IMSServiceRequester. This method is analogous to a PCB system service DL/I call, which, in addition to indicating which PSB the CICS application will use, obtains the address of the program control blocks (PCBs) in the PSB.
| serviceRequester imsBankDatabase imsAccessor | "Identify which PSB to use in CICS" serviceRequester := IMSServiceRequester new schedulePsb: 'AELBANK1' "Instantiate the IMSDBRequester class" imsBankDatabase := IMSBankDatabase new. imsAccessor := IMSDBRequester usingDBPCBAtPosition: 1. imsBankDatabase dataAccessor: imsAccessor.
Note: | CICS applications that access IMS databases must use the PCB's position; a CICS application cannot reference an IMS database using the PCB's name. |
Once the PSB is scheduled, the CICS application can use DL/I calls on the IMS database accessed through the specified PSB. See Appendix C, IMS Smalltalk classes for more information about the IMS DL/I calls available.