Minact-Scn Master-Status: Grec-Scn Messages In Trace File

Hi,

Version 11.2.0.2

I came across a situation when MMON process can generate Hugh traces in backgroud dump directory. Reason was unknown why mmon process is creating lots of traces..

Following metalink note explains reason for it.

ID 1361567.1

Tracefile contents are:

*** 2012-03-19 15:58:43.884
minact-scn master-status: grec-scn:0x0000.019ffe75 gmin-scn:0x0000.019ffe75
gcalc-scn:0x0000.019ffe75
minact-scn master-status: grec-scn:0x0000.01a00095 gmin-scn:0x0000.01a00095
gcalc-scn:0x0000.01a00095
 
*** 2012-03-19 16:08:47.655
minact-scn master-status: grec-scn:0x0000.01a0020c gmin-scn:0x0000.01a0020c
gcalc-scn:0x0000.01a0020c

Coming back to situation:

In 11g a new feature was introduced, that is called "active scn optimization feature"

.This feature was introduced to improve the "Delayed blocks cleaout operation".

Now what is block clean out operation and why it had issues prior to 11g?

Well following blog explain what is Block cleanout operation and how it happen actually.

"http://hemantoracledba.blogspot.in/2008/10/delayed-block-cleanout.html"

Solution:

Solution is to disable this feature manually by setting 

alter system set "_enable_minscn_cr"=false scope=spfile;

So if you are not having high batch job operation, disabling this wont have any effects to your database.
However if you do have high batch job and there are blocks requirements for next operation
then second operation maybe delayed a bit in doing Block cleanouts.