ECSA/ESQA fragmentation with XCOM for z/OS

Products

• XCOM Data Transport - z/OS

Issue/Introduction

The zOS team has detected problems in the system due to the fact that the ESQA memory overflows towards ECSA memory, leaving it very fragmented. This causes degradation in the performance of the system, and IPL is needed.

 

Environment

Release : 12.0

Component : XCOM Data Transport for z/OS

Cause

The storage in question is not directly allocated by XCOM, but rather is allocated when compression methods are requested which run on the zIIP processor (i.e. algorithms other than ZLIB with zEDC).

It seems that the initiation of numerous concurrent zIIP-using transfers has caused this allocation to be at a higher than normal level.

Resolution

At this point, there are two options for eliminating the fragmentation in your ECSA.

1. Set ZIIP=NO in your config members for all transfers which do not use compression.
2. Enlarge the ESQA in each of your systems so that it does not overflow into the ECSA.