Purging Unified Audit Trail in Oracle 12c R1

The Unified Audit Trail has become too big, you cannot directly delete or truncate the table. You must call the dbms_audit_mgmt.clean_audit_trail. But then you want to know if it will do slow deletes or quick truncates. Let’s trace it.

I have filled my Unified Audit Trail with hundred of thousands failed logins:

We have two methods to purge: purge records older than a timestamp or purge all.

Purge old

Auditing is different than logging. It’s a security feature. The goal is not to keep only recent information by specifying a retention. The goal is to read, process and archive the records, and then set a timestamp to the high water mark that has been processed. Then a background job will delete what is before this timestamp.

I set the timestamp to 6 hours before now

And call the clean procedure:

Purge all

I have still lot of rows remaining.

When purging all without setting a timestamp, I expect a truncate which is faster than deletes. Let’s try it and trace it.

Note:

Cleaning the Unified Audit Trail is done with internal statements but looks like a delete when use_last_arch_timestamp=TRUE or a truncate when use_last_arch_timestamp=FALSE. This means that we can use this procedure when AUDSYS has grown too much. However, there are a few bug with this internal table, partitioned even when partitioning is not allowed. The implementation has changed in 12.2 so the next blog post will show the same test on 12cR2.

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