DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

► Larger VSAM CI sizes: DB2 V8 introduces support for VSAM CI sizes of 8, 16, and 32
KB, which potentially reduces the elapsed time for all I/O bound workloads.
► Instrumentation enhancements: Significant enhancements to DB2 instrumentation have
been added in V8.
► Miscellaneous items:
– DB2 logging enhancements: DB2 V8 increases the amount of active log data set pairs
from 31 to 93, as well as increases the number of archive log data sets from 1,000 to
10,000. This enhancement increases the amount of log data DB2 has available online
for recovery, which can have a dramatic impact on recovery performance and data
availability.
– Up to 65,041 open data sets: DB2 V8 increases the number of open data sets from 32k
to 65,041 by exploiting z/OS 1.5 which allows open data set control blocks to be
allocated above the 16 MB line. This enhancement does not only provide virtual
storage relief, it also removes a potential scalability problem with growing systems and
growing machine capacity.
– SMF Type 89 record collection enhancements: DB2 V8 provides a new DSNZPARM
parameter, SMF89, which lets you specify whether or not DB2 is to do detailed tracking
for measured usage pricing. Previous releases of DB2 automatically used detailed
tracking of measured usage if SMF type 89 records were activated. This is available in
CM.
– Lock avoidance enhancements: DB2 V8 avoids taking locks on overflow records if a row
has been relocated to another page. In addition, DB2 performs lock avoidance for
singleton SELECT statements with ISOLATION(CS) and CURRENTDATA(YES). This
is available in CM.
128 DB2 UDB for z/OS Version 8 Performance Topics