Mainframe, MVS and zOS Discussion

Hello People!!

How to know when I need to reorganize tables?
A systems analyst told me that the system performance is poor. And asked me to reorganize tables. How to know which tables should be reorganized without knowing what programs are with the poor performance??

Thanks a lot!!

DB2 Tables REORG and performance tuning of programs involved are two different things. Said that, if you're talking about DB2 on z/OS - read about DB2 RUNSTATS Utility.

According to the above link:

Run RUNSTATS to help evaluate the design of the database and determine when the REORG utility should be run for specific table spaces or indexes.

This is another link on RUNSTATS, which gives more explanation about it.

A very good link here to start with REORG

Maidy,

To add here, you not only re-organize tables but also re-organize indexes! As time goes by, insertions and deletions can cause tables, indexes to be dis-organized. In brief, REORG's put table data on the pages in order(clustering sequence). Free-space is reset. DB2 maintains real-time statistics about tables/indexes in SYSTABLESPACESTATS and SYSINDEXSPACESTATS. Explore these.

Thanks,
Quasar C.

Hello Quasar. Thanks for your consideration!

The REORG TABLESPACE command reorganizes all data and all indexes tied to it.

Txs!
Maidy

Yes indeed! Cool.