How Does FBDA Operate And How Can We Manage The Workload Better
(Doc ID 2101765.1)
Last updated on JUNE 17, 2020
Applies to:Oracle Database - Enterprise Edition - Version 18.104.22.168 and later
Oracle Database Cloud Schema Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.
Over the last 2+ years, we have utilized Oracle Total Recall (FBDA) to keep a history of changes for many tables in our main database. During that time, we've experienced quite a few performance problems and have worked with Oracle support to gather information and have gotten patches to correct issues, when needed. During this time, as part of various SRs, I have asked for information on how FBDA does its processing and have not gotten a complete answer. I would like to formally request more information on how FBDA does its work.
1. From what I can tell, when data is modified in an FBDA-enabled table, the changes are registered in a temporary system table. That data is then merged into another temporary system table and deleted from the first one. After this, the data is merged into the main system FBDA table and deleted from the previous temp table. Is this correct?
2. What triggers the processing of data through the path laid out in #1? We see an FBDA process that runs and will run some statements, but we also see MERGE, DELETE, and INSERT statements against the FBDA tables run by application sessions. How and why are those run? Does that happen every time a modification to an FBDA-enabled table occurs?
3. Are records written to the FBDA system table when inserting records? There is some confusion here on this.
4. Why would the processing of FBDA records cause contention and waits for the main table? How can we reduce that?
5. How can we control when the management of the FBDA data happens? What triggers the processing? Time? Amount of changes? Something else? Can that be tuned? Is it possible to delay the processing until after hours?
Thank you for your help in getting answers for these questions.
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