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Undo tablespace / Expired and Unexpired

edited Dec 9, 2015 10:04AM in Database Administration (MOSC) 3 commentsAnswered

Oracle: 11.2.0.4

DB size: 5 TB

Undo_management = Auto

Undo Tablespace Size: 202 GB

undo_retention = 1800 (1/2 hour)

I adjusted this parameter from 28,800(8 hours) to 1800(1/2 hour) 5 + hours ago.

We run our data load(DML) by early morning.

The DBA_UNDO_EXTENTS shows, Expired = 40 GB and Unexpired =136 GB and no Active.

1. Why does the Expired(40 GB) + Unexpired(136 GB) does not add up to 202 GB - the total Undo Tablespace size.

2. 5+ hours ago when I changed the Undo_Retention to 1800 seconds(1/2 hours) and no DML for last 6+ hours, I was expecting the Unexpired = close to zero. I don't understand this behavior.

3. how do we regain space that unexpired is still holding after 1800 seconds?

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