DIRCA= parameter for procedures

Use the DIRCA= parameter in procedure to specify the size of the dependent region interregion communication area (DIRCA). The size specified must be a 3-digit number (for example, 001).

The size specified represents the number of 1 KB blocks of subpool 251 to be reserved to hold a copy of your PCBs.

If you do not specify a DIRCA size, or if you specify a size of 000, IMS uses the system default for this message region. The size of the system default, determined during system initialization, is the maximum size required for any PSB. If necessary, IMS updates this default when an online change is made or when a dynamic PSB is scheduled.

Normally, you should not specify this parameter. You can use it to reduce the DIRCA size for a region where only PSBs with small DIRCA requirements are scheduled by class scheduling.

The output from message DFS0589I occurring during ACBGEN facilitates DIRCA size calculation. Each PSB has a PCB=value that is the sum of the PCBs within it. The PCB value plus 64 is the required DIRCA size, in bytes.

The Fast Path utility program uses a PSB that contains an I/O PCB and a DB PCB for the DBD specified in the JCL parameters. A DIRCA size of 002 is sufficient to contain the control blocks built for the PSB.