CEMT SET DSAS

Change the system storage attributes for dynamic storage areas (DSAs) below 16 MB and DSAs above 16 MB but below 2 GB.

In the CICS Explorer, the Global Dynamic Storage Areas operations view provides a functional equivalent to this command.

Syntax

Press the Clear key to clear the screen. There are two ways to start this transaction:
  • Type CEMT SET DSAS (or suitable abbreviations for the keywords). The resulting display shows the current status, similar to that obtained by using the CEMT INQUIRE DSAS command. You can tab to the highlighted or blank fields and overtype them with the required values.
  • Type CEMT SET DSAS (or suitable abbreviations for the keywords), followed by one or more attribute settings that you want to change. For example, cemt s dsa ds(value) ed(value) resets the value for dynamic storage below 16 MB (below the line) and the value for dynamic storage above 16 MB but below 2 GB (above the line).

Typing ? at the beginning of either the first or second line gives a syntax prompt. Resetting the values takes effect immediately.

CEMT SET DSAS

Read syntax diagramSkip visual syntax diagramCEMT SET DSASDSALIMIT( value)EDSALIMIT( value)

Options

DSALIMIT(value)
Specifies the maximum amount of storage, as a total number of bytes, within which CICS® can dynamically allocate storage for the four individual DSAs that reside below 16 MB (below the line). For more information, see DSALIM system initialization parameter. If DSALIMIT specifies a value lower than the current limit, CICS might not implement the new limit immediately, but attempts to do so over time as dynamic storage is freed in the individual DSAs.
EDSALIMIT(value)
Specifies the maximum amount of storage, as a total number of bytes, within which CICS can dynamically allocate storage for the individual DSAs that reside above 16 MB but below 2 GB (above the line). For more information, see EDSALIM system initialization parameter. If EDSALIMIT specifies a value lower than the current limit, CICS might not implement the new limit immediately, but attempts to do so over time as dynamic storage is freed in the individual DSAs.
Note: That while you are changing the DSA and EDSA limits dynamically is possible, it is recommended that you do not do so unless you are addressing an urgent situation and are trying to avoid cycling the region. While your change to the DSA and EDSA limits might be successful from the CICS perspective, increasing the limits can cause other problems because the larger DSA/EDSA will no longer be contiguous. MVS™ allocates storage both from high private growing down, and low private growing up. Increasing the DSA/EDSA limits dynamically will cause a new piece of storage that is allocated by CICS in the middle of the MVS private storage area. Depending on the MVS use of storage in this area, you might now be at increased risk of an S878 or S80A abend as a result.

Similarly, decreasing the DSA/EDSA limits dynamically might indeed give back storage to MVS for use, but there is no certainty where the storage given back will be, and it most likely will not be in an area where MVS needed it.

Monitor CICS statistics regularly, and proactively adjust DSA/EDSA limits, and MXT limits.