Datacom MUF abend in IBM IOS module IECVEXSM

Products

• Datacom
• Datacom/DB
• Datacom/AD

Issue/Introduction

One of the following messages can be found on the Datacom Multi-User Facility (MUF) joblog:
DUMP TITLE=COMPON=EXCP - STORAGE MANAGER ,COMPID=SC1C6,ISSUER=IECVEXSM,IECVSMFR,PROGRAM ERROR                      
or 
DUMP TITLE=COMPON=EXCP - STORAGE MANAGER ,COMPID=SC1C6,ISSUER=IECVEXSM,IECVSMFR,ABEND= C0D   
but the region doesn't crash.

Environment

Z/OS

Datacom 15.0 - applications performing GETIT processing

Cause

The problem is actually in the IBM code and it occurs when one or more applications are actively performing GETIT processing, which causes sequential read-ahead in MUF. 

Resolution

IBM APAR OA56384 (title: ABEND C0D IN IECVEXSM ABEND 0C4 IN IECVEXSM) has been opened for this problem. The related IBM PTF must be applied to solve the error.

Additional Information

Workaround: if the IBM PTF cannot be applied, the Read-ahead feature of Datacom sequential processing can be disabled using the console-like command:
DIAGOPTION 17,1,ON
To enable it again, the following command must be issued:
DIAGOPTION 17,1,OFF

NOTE: Disabling this feature could adversely affect the performance of the applications using sequential commands, as Read-ahead is a sort of "prefetch" that can reduce the number of I/O operations.

In order to use these console-like commands, Datacom/DB 15.0 SO05768 must be applied.