AIX 6.1
DB2 9.7 FP 5
Recently we had performance issue with a query. We analysed the query and found that it going for tbscan as index was not present on predicates of query.
We created an index on those predicates.
index creation was followed by runstats on table as well indexes.
after rerunning the query we observe that db2 still did not use the index.
We were confused as this was a simple query .
we checked the defragmentation of table in question using reorgchk however it found it okay.
Left with no choice and to improve the disk i/o performance in case of tbscan we decided to do the reorg. After reorg got completed, we ran the query and it started using the index!
Question
1) DB2 might have reasons to not use index before reorg however my question is how to identify this.
2) is reorgchk always accurate in what it tells. if not is there any other way to check defragmentaion of table.
DB2 9.7 FP 5
Recently we had performance issue with a query. We analysed the query and found that it going for tbscan as index was not present on predicates of query.
We created an index on those predicates.
index creation was followed by runstats on table as well indexes.
after rerunning the query we observe that db2 still did not use the index.
We were confused as this was a simple query .
we checked the defragmentation of table in question using reorgchk however it found it okay.
Left with no choice and to improve the disk i/o performance in case of tbscan we decided to do the reorg. After reorg got completed, we ran the query and it started using the index!
Question
1) DB2 might have reasons to not use index before reorg however my question is how to identify this.
2) is reorgchk always accurate in what it tells. if not is there any other way to check defragmentaion of table.
