Implementing an XEIIN global user exit

The XEIIN global user exit can be useful if an overlay is not being detected until CICS® task termination is doing the final freeing of storage. CICS can detect a Storage Accounting Area (SAA) overlay either during an explicit FREEMAIN or during task termination. If detected at task termination, the task is not abended by CICS and hence Z Abend Investigator is not invoked. CICS attempts to take a system dump, with dump code SM0102, however if CICS system dumps are being suppressed, further analysis is not possible.

To assist with SAA overlays Z Abend Investigator provides a program that can optionally be installed in the XEIIN global user exit. If installed, this program, at each EXEC CICS RETURN statement, validates all the CICS storage accounting areas for the current task. If an overlay is found, then one of two actions can be performed:

  1. A call can be made to take a CICS transaction dump with dumpcode HFZS.

    If Z Abend Investigator is installed in the XDUREQ global user exit, then this transaction dump is analyzed in the normal manner with a history file fault entry being created.

  2. An SDUMP of the CICS region can be taken.

    The request to take this SDUMP is made by the HFZS subsystem, and as such, it is not affected by the CICS system dump suppression setting. If a SDUMP is captured, then it can then be analyzed interactively by way of the File menu option 5.

Enabling the Z Abend Investigator XEIIN global user exit program, and setting which action should be performed, is done using the Z Abend Investigator supplied CFA transaction. Unlike the other Z Abend Investigator CICS exits, there is no option to enable the XEIIN exit during CICS PLT processing.

When invoked, the initial CFA display is similar to the following:

                   Z Abend Investigator Control Transaction                        
Options: I=Install U=Uninstall                                               
                  Current Status/Error Message                               
_ XPCABND         Installed                                                  
_ XDUREQ          Installed                                                  
_ LE Exit         Installed                                                  
_ SDUMP Screening Installed                                                  
_ XEIIN           Uninstalled   
                                                                             
        Current    HWM  Setting    MWS                                       
Active     0000   0001     0001                                              
Waiting    0000   0000     0017   0000                                       
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
HFZTRACE OFF DeferredReport ON                                               
                                                                             
PF1=Help PF3=Exit PF4=Opts PF5=Clear FND Area PF9=IVP PF11=TRACE ENTER=Update

From this display, an "I" can be entered next to XEIIN to install the exit. A screen similar to the following is then displayed:

                   Z Abend Investigator Control Transaction                        
Options: I=Install U=Uninstall                                               
                  Current Status/Error Message                               
_ XPCABND         Installed                                                  
_ XDUREQ          Installed                                                  
_ LE Exit         Installed                                                  
_ SDUMP Screening Installed                                                  
_ XEIIN           Installed   N TXN dump N SDUMP Set at least one option to Y
                                                                             
        Current    HWM  Setting    MWS                                       
Active     0000   0001     0001                                              
Waiting    0000   0000     0017   0000                                       
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
                                                                             
HFZTRACE OFF DeferredReport ON                                               
                                                                             
PF1=Help PF3=Exit PF4=Opts PF5=Clear FND Area PF9=IVP PF11=TRACE ENTER=Update

In this screen, enter "Y" next to either TXN dump or SDUMP to set the action to take when an SAA overlay is detected.

The I (Install) option must be used each time the TXN or SDUMP field is changed.

Note: Although there is no overhead in having any other Z Abend Investigator exit installed/enabled, the XEIIN exit is invoked by CICS on every EXEC CICS command, and hence does incur a small overhead. As such, it is recommended to only use the XEIIN exit when needing to investigate SAA overlays.