agburke 060001QPDN Visits (3483)
This APAR concerns customers who partition table spaces based on a timestamp column. When this customer moved to DB2 10 this query lost the ability to prune partitions on a partitioned table space and the response time increased dramatically. In this case the application was comparing the timestamp column to a host variable with a timestamp precision (6). The temporary fix is to use PLANMGMT to fall back to the previous access path.
· PM81692 – performance degradation for table partitioned on timestamp
This APAR deals with table insert experiencing longer than expected space search times. This can occur when the clustering index does not provide an adequate position for insert within the table.
· PM75921 – long insert times due to inadequate search for free space in the clustering index
agburke 060001QPDN Visits (3235)
Since V9 of DB2 we have allowed the ACCESS DB MODE(OPEN) to allow customers to prime buffer pools with objects that will be opened by, for instance, the first application execution of the day. This command showed poor performance previously as it was single threaded. In the next version of DB2 this will be done in parallel, so we have retrofitted it back to DB2 10.
· PM80779- ACCESS DB performance improvement
flodubois 270000K6H5 Visits (2847)
Updated Technote: What is DB2 Accounting Class 2 Not Accounted Time?
Question:What is DB2 Accounting Class 2 Not Accounted Time?
See the recently updated list of probable causes in the following Technote
Michael_D. 1100004WAH Visits (5494)
DB2 10 can reduce the total DB2 CPU demand from 5-20% when you take advantage of all the enhancements. Many CPU reductions are built in directly to DB2, requiring no application changes. Some enhancements are implemented through normal DB2 activities through rebinding, restructuring database definitions, improving applications, and utility processing. The CPU demand reduction features have the potential to provide significant total cost of ownership savings based on the application mix and transaction types.
Improvements in optimization reduce costs by processing SQL automatically with more efficient data access paths. Improvements through a range-list index scan access method, list prefetch for IN-list, more parallelism for select and index insert processing, better work file usage, better record identifier (RID) pool overflow management, improved sequential detection, faster log I/O, access path certainty evaluation for static SQL, and improved distributed data facility (DDF) transaction flow all provide more efficiency without changes to applications. These enhancements can reduce total CPU enterprise costs because of improved efficiency in the DB2 10 for z/OS.
DB2 10 includes numerous performance enhancements for Large Objects (LOBs) that save disk space for small LOBs and that provide dramatically better performance for LOB retrieval, inserts, load, and import/export using DB2 utilities. DB210 can also more effectively REORG partitions that contain LOBs.
This IBM Redbooks® publication® provides an overview of the performance impact of DB2 10 for z/OS discussing the overall performance and possible impacts when moving from version to version. We include performance measurements that were made in the laboratory and provide some estimates.
Keep in mind that your results are likely to vary, as the conditions and work will differ.
In this book, we assume that you are somewhat familiar with DB2 10 for z/OS.
See DB2 10 for z/OS Technical Overview, SG24-7892-00, for an introduction to the new functions.
Michael_D. 1100004WAH Visits (5552)
PM31614: PERFORMANCE OF PACKAGE ALLOCATION IMPROVEMENT http
Some of the code was moved to a service task to reduce the CPU time required for packages that have a very short
running SQL statements or that issue frequent commits.
Michael_D. 1100004WAH Visits (4835)
Higher CF CPU utilization in a DB2 10 for z/OS data sharing environment during Delete_Name processing. Delete_Name requests/sec can be significantly higher in DB2 10 for z/OS than in DB2 9 for z/OS. In V10, when the pageset/partition becomes non GBP dependent, the Delete_Name process deletes only data entries to avoid cross invalidation processing at that time, and to allow cleanup of the directory
entries later when other pages are registered. The V9 Delete_Name process deleted both data and directory entries. In DB2 10 for z/OS, the Delete_Name requests/sec can be significantly higher because CFCC processing is not as efficient when only data entries are deleted.
PM51467: CF DELETE_NAME PERFORMANCE IN DB2 10 FOR Z/OS http
Michael_D. 1100004WAH Visits (4971)
System z Integrated Information Processor (zIIP)
The IBM zIIP is available on all IBM zEnterprise, IBM System z10 and IBM System z9 servers. The zIIP can support many technologies, and can help implement, integrate, and optimize new workloads on System z.
DB2 z/OS zIIP related performance:
PM12256: DRDA PERFORMANCE IMPROVEMENT USING TCP/IP
OA35146: NEW FUNCTION - ALLOW NON-CLIENT PREEMPTABLE SRBS TO JOIN/LEAVE AN ENCLAVE AFTER IT HAS BEGUN – z/OS APAR for PM12256PM2
DB2 z/OS informational APAR II14219 (DB2 z/OS ZIIP EXPLOITATION "SUPPORT USE" INFORMATION)