High 'CELL SMART TABLE SCAN' latency after patching storage cells to 22.1.28 or higher, 23.1.17 or higher, or 24.1.X (Doc ID 3071057.1)

Last updated on MARCH 26, 2025

Applies to:

Symptoms

Exadata systems hosting multiple workload-intensive databases with storage cells with specific Exadata Storage software versions may experience significant performance degradation in smart scan performance immediately post-upgrade/deployment.
The issue can affect customers on all platforms (i.e. onprem or cloud - ExaDB-D, ExaDB-C@C, ExaDB-XS).

Symptoms include:

• Exadata Storage software version is upgraded to 22.1.28 or higher, 23.1.17 or higher, or 24.1.X
• Smart scan performance issues with high IORM flash queue time.
• The evidence is seen in AWR under:
        'Top Timed Events': where the 'cell smart table scan' wait event is very high.
        'Top Databases By Requests - Details': Under 'Large Requests' the flash queue time is showing very high.

• AWR ("top database" section) reports high latency and queue time for the large IOs hitting the flash as seen above.

• From CellSrvStatExaWatcher log check the below:
        Small IO protection is kicking, which is queuing the large IOs in flash and the NO IOs issued due to max device queue depth.

===Current Time=== Thu Nov 21 15:52:29 2024
No IO issued due to max device queue depth 18064 406468328
No IO issued to protect small IO latency 126806 954066377
No IO issued to protect large IO latency 0 0

===Current Time=== Thu Nov 21 15:52:35 2024
No IO issued due to max device queue depth 309788 406778116
No IO issued to protect small IO latency 154167 954220544
No IO issued to protect large IO latency 0 0

===Current Time=== Thu Nov 21 15:52:40 2024
No IO issued due to max device queue depth 217105 406995221
No IO issued to protect small IO latency 148456 954369000
No IO issued to protect large IO latency 0 0

Changes

Exadata Storage software version is upgraded to 22.1.28 or higher, 23.1.17 or higher, or 24.1.X

Cause

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