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Query Execution Plan Changed After UpgradingDG4DRDA From To Causing Increased Execution Times (Doc ID 1681234.1)

Last updated on FEBRUARY 25, 2022

Applies to:

Oracle Database Gateway for DRDA - Version to [Release 11.2 to 12.1]
Information in this document applies to any platform.


The query execution plan for a particular query against several DB2 tables changed after upgrading the Database Gateway for DRDA (DG4DRDA) from to
After the gateway upgrade the SQL against the DB2 tables had a different execution plan -
- In, the execution plan sent a complete query to DB2 for all the tables and results were returned in 30 minutes
- In, the execution plan causes queries against individual DB2 tables on the DB2 side. There is then join made on the Oracle side of the individual table results. Because the underlying DB2 tables are large, the query now runs for over 4 hrs.

- In and you can receive the ORA-28501: communication error on heterogeneous database link 


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