Database Tuning (MOSC)

MOSC Banner

Transaction block consistent read are high after upgrade to 12c database

edited Dec 3, 2019 4:00AM in Database Tuning (MOSC) 4 commentsAnswered

we upgraded our database from 11gr2 to 12cR1 last year. As soon as after the upgrade. Our Queries started to run longer. And it was never ending. The plan and wait events looked similar.

So what changed?  We did our analysis and found out that the queries are reading data from undo.  And found it to be delayed block cleanout with stats type - Transaction block consistent read- undo records applied.

We the set the _rollback_segment=2000 AUM. After setting the value the undo issue somehow reduced. but not completely. Something has changed in 12c undo management feature which is sadly effecting us badly.

Howdy, Stranger!

Log In

To view full details, sign in to My Oracle Support Community.

Register

Don't have a My Oracle Support Community account? Click here to get started.

Category Leaderboard

Top contributors this month

Instructions for posting

×

1. Select a discussion category from the picklist.


2. Enter a title that clearly identifies the subject of your question.


3. In the body, insert detailed information, including Oracle product and version.


Please abide by the Oracle Community guidelines and refrain from posting any customer or personally identifiable information (PI/CI).


Cloud / Fusion customers - Our Cloud community has moved! Please go to Cloud Customer Connect .


New to My Oracle Support Community? Visit our Welcome Center

MOSC Help Center