High Number of Child Cursors for Queries using SPM due to HASH_MATCH_FAILED
Last updated on JUNE 16, 2017
Applies to:Oracle Database - Enterprise Edition - Version 22.214.171.124 and later
Information in this document applies to any platform.
- High version counts for many queries with HASH_MATCH_FAILED:
By definition, HASH_MATCH_FAILED means that no existing child cursors have the unsafe literal bind hash values required by the current cursor.
In such cases the query executed contains TIMESTAMP column. The TIMESTAMP column is marked as a none data literals so we are generating different hash for each none data literals each time function "Search Child List" is called and that's why the different child is created due to hash-mismatch(HASH_MATCH_FAILED=YES).
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