Program storage

The level of program storage in use is incremented at each program LOAD, LINK, and XCTL event by the size (in bytes) of the referenced program, and is decremented at each program RELEASE or RETURN event.

Note: On a program XCTL event, the program storage currently in use is also decremented by the size of the program issuing the program XCTL because the program is no longer required by the task.

Figure 1 shows the relationships between the high-water mark data fields that contain the maximum amounts of program storage in use by the user task. Field PCSTGHWM (owner: DFHSTOR, field ID: 087) contains the maximum amount of program storage in use by the task both above and below the 16MB line. Fields PC31AHWM (owner: DFHSTOR, field ID: 139) and PC24BHWM (owner: DFHSTOR, field ID: 108) are subsets of PCSTGHWM, containing the maximum amounts of program storage in use above and below the 16MB line, respectively. Other program storage fields, which are also a subset of PCSTGHWM, contain the maximum amounts of program storage in use by the task in each of the CICS® dynamic storage areas (DSAs).

Note: The totaled values of all the subsets in a superset might not necessarily equate to the value of the superset. For example, the value of PC31AHWM plus the value of PC24BHWM might not equal the value of PCSTGHWM. This is because the peaks in the different types of program storage acquired by the user task do not necessarily occur simultaneously.
The program storage high-water mark fields are described in detail in DFHSTOR program storage fields.
Figure 1. Relationships between the high-water mark program storage data fields
      PCSTGHWM - high-water mark of program storage in all CICS DSAs
       ┌──────────────────────────────────────────────────────────┐
       │                                                          │
       │         PC31AHWM - HWM of PC storage above 16MB          │
       │                                                          │
       │                ┌───────────────────────┐                 │
       │                │ PC31CHWM - ECDSA HWM  │                 │
       │                ├───────────────────────┤                 │
       │                │ PC31SHWM - ESDSA HWM  │                 │
       │                ├───────────────────────┤                 │
       │                │ PC31RHWM - ERDSA HWM  │                 │
       │                └───────────────────────┘                 │
       │16MB line                                                 │
       ├──────────────────────────────────────────────────────────┤
       │                                                          │
       │         PC24BHWM - HWM of PC storage below 16MB          │
       │                                                          │
       │                ┌───────────────────────┐                 │
       │                │ PC24CHWM - CDSA HWM   │                 │
       │                ├───────────────────────┤                 │
       │                │ PC24SHWM - SDSA HWM   │                 │
       │                ├───────────────────────┤                 │
       │                │ PC24RHWM - RDSA HWM   │                 │
       │                └───────────────────────┘                 │
       │                                                          │
       └──────────────────────────────────────────────────────────┘