Degrading system performance caused by snapshot execution

Detail name	Value
Changelog Number	11748
Type	Bug
Status	Resolved
Affected Versions	Exasol 6.2.0, Exasol 7.0.0, Exasol 7.1.0
Fix Versions	Exasol 7.1.0, Exasol 6.2.14, Exasol 7.0.9
Resolution Date	2021-04-08

Description

System performance may gradually degrade in the following situations:

• A query is executed in snapshot mode within a regular transaction (including most metadata requests using API calls in ODBC and JDBC)
• A query is executed in snapshot mode (see EXASOL-2646) and fails with an exception

In both cases, the memory footprint from the snapshot locks may persist, which causes a degradation in the overall performance of transactions.

Transaction consistency is not affected.

Workaround

Restart the database.

Fix

The memory footprint is freed as soon as possible, which removes the performance degradation.