Storage recommendations

The real-time execution following an abend requires extra storage in the abending region while the analysis is carried out on the in-storage data.

The following are the minimum requirements for the available region size, assuming that neither Language Environment®, nor Z Abend Investigator, are available from LPA:
  • A minimum of 440 kilobytes below-the-line (24-bit) storage, regardless of execution environment.
  • A minimum of 35 megabytes above-the-line (31-bit) storage for CICS® transactions.
  • A minimum of 33 megabytes above-the-line (31-bit) storage for programs other than CICS transactions.

Depending on the type of fault being analyzed, and the environment in which this fault occurs, more storage might be required.

The storage requirements under CICS are for MVS™ GETMAIN-managed storage, not CICS DSA-managed storage. So, to increase below-the-line MVS GETMAIN-managed storage, you would need to decrease CICS below-the-line DSA-managed storage (and similarly for above-the-line storage).

Information about the actual storage used by Z Abend Investigator is available at the end of the real-time analysis report. However, the amount of storage provided in the report accounts for the explicit allocations performed by Z Abend Investigator only and does not include, for example, Language Environment heap and stack storage or storage used for load modules.

In post-abend situations, where the minidump or associated MVS dump data set is being processed, only a marginal increase in storage requirements occur over that of the real-time execution, as the result of allocating space for referenced dump pages. The increase is typically less than 500 kilobytes.

For interactive reanalysis, the storage is required in the TSO region.

The minimum available region size above-the-line can be reduced by the size of required modules that are either available from LPA (and therefore do not need to be loaded), or those that are already loaded, if, for example, the abending program uses LE.

Having LE in LPA saves around 8 megabytes, and Z Abend Investigator in LPA around 13 megabytes, reducing the storage requirement for a typical non-CICS program to around 12 megabytes.

If the necessary below-the-line (24-bit) size is not available, message HFZ0086E is issued and processing terminates.

If the necessary above-the-line (31-bit) size is not available, message HFZ0055E is issued and processing terminates. Message HFZ0087I might also be issued to provide information about storage that could be made available if the command included in the message text is issued to add modules to LPA. The module names likely to be included in the message are the Z Abend Investigator module HFZDA and HFZLANGX. To place these modules in LPA, and save approximately 14 megabytes above-the-line (31-bit) storage, either issue the following MVS operator command:
SETPROG LPA,ADD,MOD=(HFZDA,HFZLANGX),DSN=LNKLST
or add HFZ.SHFZLPA1 to the LPALSTxx parmlib member (for details, see Making Z Abend Investigator modules available).

The MVS IEFUSI exit can be used as a general way to provide a larger region size if JCL change is not practical for all jobs. A sample IEFUSI exit is provided as member HFZSUSI in the HFZ.SHFZSAM1 data set. The exit increases the region size of all jobs by 16 megabytes. Refer to the comments in the sample for details about how to install the exit.