IBM Support

Database indexes are sometimes not used by the Oracle optimizer thus causing full table scans and slow running queries

Troubleshooting


Problem

We have observed (both in-house and customer environments) slow running queries in some cases where the Oracle optimizer is not using the database indexes available and is performing full table scans on a CE table (e.g., DocVersion). Oracle has identified an issue with Oracle 10g in one case where the stats were incorrect when using the dbms_stats.gather_schema_stats default parameters. In another case using the DBMS_STATS.GATHER_DATABASE_STATS_JOB_PROC, which gathers stats for tables with empty or stale statistics, may have resulted in a non-optimal query plan because running a dbms_stats command with explicit parameters remedied the issue at a customer site.

Symptom

Slow queries with table scans instead of the available indexes being used.

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Document Information

Modified date:
28 April 2025

UID

swg21468281

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