Starting the DL/I separate address space

If you choose to use a DL/I separate address space, use the DLINM= keyword in the DFSPBxxx member to identify the name of the DLISAS procedure that IMS is to start. Some situations require that the DLISAS procedure by modified, and exit routines that run in the DLISAS have restrictions.

After opting to use a DLISAS by specifying LSO=S on the IMS procedure, use the DLINM parameter of the IMSCTRL macro to specify the name of the DLISAS procedure to start. Unless you change that name, this is the name of the DLISAS procedure that IMS tries to start. You can override this name using DLINM= in the DFSPBxxx IMS PROCLIB data set member that is used to start IMS.

The skeletal procedure DLISAS is built during SMP/E processing and users can copy the DLISAS procedure from the IMS.SDFSPROC to the IMS.PROCLIB data set. Modify this procedure as necessary so that the variable names match what they would have been if generated by Sysgen. Copy the procedure to the SYS1.PROCLIB data set.

Modifying the DLISAS procedure

The following modifications to the DLISAS procedure might be required:

  • The JCL DD statements for the full-function databases must be in the DLISAS procedure, not in the IMS procedure. JCL DD statements for Fast Path databases and the IMS system data sets remain in the IMS procedure.
  • The specification of the active and inactive ACBLIBs must be identical in both the IMS procedure and the DLISAS procedure. Both the control region and the DLISAS read the ACBLIB. The data sets used must have shared disposition (DISP=SHR), and the concatenation order must be identical.

    These ACBLIB data sets can be dynamically allocated by using the DFSMDA member.

  • The IMS PROCLIB data set must be defined in both the IMS and DLISAS procedures.

The only parameters passed on the DLISAS procedure are the region type (DLS) and, optionally, the IMSID of the control program to be connected. Pool sizes and database buffering options are specified on the IMS start procedure.

No changes to the dynamic allocation parameter lists in IMS.SDFSRESL are required.

Exit routines running in the DLISAS

Exit routines that run in the DLISAS are entered in cross-memory mode. These exit routines have the following restrictions:

  • The DL/I exit routines cannot address storage in the control address space.
  • If the DL/I exit routines use the IMS ISWITCH service, they must be changed. A macro specification of TO=DLI, not TO=CTL, must be specified on ISWITCH. The TO=DLI specification performs correctly in all IMS configurations.