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Question and Answer

Chris Saxon

Thanks for the question, Vickey.

Asked: February 12, 2019 - 12:20 pm UTC

Last updated: February 12, 2019 - 5:40 pm UTC

Version: 12c

Viewed 1000+ times

You Asked

We observed frequent wait event 'enq HW - contention' in performance reports with SQL includes LOB Objects.

Lob object Details –

Object - WF_WORKFLOW
Owner - IBMUCD


What changes we can face if we convert LOB from basic to secure?
What are the pre checks to be done ?
Is there any impact on data of the application?


Thanks

and Chris said...

Are you sure the LOBs are the cause of this issue?

In any case, migrating to securefiles is a good idea. Securefiles support more features including compression, deduplication, and encryption. (Though these options have licensing implications)

And basicfiles will be deprecated in the future.

https://docs.oracle.com/en/database/oracle/oracle-database/18/adlob/introduction-to-large-objects.html#GUID-67FBC558-69AC-4BCC-80B5-F2961283A4A8

You can do an online migration from basicfile to securefile using dbms_redefinition. You will need space to store a copy of the whole table though. And rebuild any global indexes.

You can find a worked example and further discussion in the docs:

https://docs.oracle.com/en/database/oracle/oracle-database/18/adlob/using-oracle-LOBs-storage.html#GUID-95FB6968-59BA-436F-ABEB-F6FA6DD5584F

The application will be able to read and write the data after the migration the same as before.

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