Thank you for such as productive topic. Based on experience you’ve carried out analyzing GC performance, when you encounter poor performance in the GC, which causes are the most common and how did you get rid of them?

Thanks in advance,

An Ng

Thanks
Riyaj

Thank you so much for the explanation. It helps a lot to understand this.
May I know which Oracle documentation also explain about this? (if exist)

Thank you,
Adhika

In RAC, When a session opens an access request for a buffer, the request will include SCN version of the block required. If there are pending transactions in the block in remote cache, then LMS process in the remote instance will apply undo records to create a consistent version of the block and then ship the block to the requestor. This is known as CR transfer.
Current buffer means, that buffer includes latest changes, i.e. it is current. SELECT statement can access current mode buffers also, (1) if the buffer version in the memory and the block version in the disk are the same. (2) Buffer contains latest changes with no pending transactions.
Obviously, application changes only happen in current mode buffers even if there are many outstanding transactions in that block already. Row level locking mechanism protect session stepping at each other.

In a nutshell, CR mode buffers are use-and-throw buffers as the CR mode buffers are created consistent at a specific SCN. Current mode buffers contains all latest changes and it is this mode buffer that can be written to the disk. CR mode buffers can not be written to the disk and they are transient. (may or may not have pending transactions).
Hope this helps.
Cheers
Riyaj

What is the difference between CR and Current? What are their relations?

Thank you so much for the scripts.

Thanks,
Adhika

Cheers
Riyaj

What version?

SQL> @awrrpt_all_gen

awrrpt_all_gen.sql v1.00 by Riyaj Shamsudeen @orainternals.com

To generate AWR Report from all RAC instances concurrently.

Creates reports using last two snap_ids.

…Generating awrrpt_all.sql script…. Please wait…. …Completed script generation.

Executing awrrpt_all.sql to generate AWR reports. …Generates AWR reports with file name format awrrpt___.txt for each instance. …Please wait for few minutes…

…AWR report created for instance 1. Please wait.. AWR reports created. SQL> @awrrpt_all_gen

awrrpt_all_gen.sql v1.00 by Riyaj Shamsudeen @orainternals.com

To generate AWR Report from all RAC instances concurrently.

Creates reports using last two snap_ids.

…Generating awrrpt_all.sql script…. Please wait…. …Completed script generation.

Executing awrrpt_all.sql to generate AWR reports. …Generates AWR reports with file name format awrrpt___.txt for each instance. …Please wait for few minutes…

…AWR report created for instance 1. Please wait.. AWR reports created.

Cheers

Riyaj Shamsudeen Principal DBA, Ora!nternals – http://www.orainternals.com Specialists in Performance, Recovery and EBS11i Blog: http://orainternals.wordpress.com OakTable member Oracle ACE Co-author of the book”Expert Oracle Practices” http://tinyurl.com/book-expert-oracle-practices

Just got confused..i executed the script first time it generated the output..and executed again i didnt generate a output..

First time

SQL> set termout off
SQL> set serveroutput on
@awrrpt_all.sql
SQL> set termout on
set pagesize 24
PROMPT AWR reports created.
set serveroutput off
…AWR report created for instance 1. Please wait..
SQL> SQL> SQL> AWR reports created.
SQL> SQL>

second time when i executed the same script..it doesnt generate..

SQL> PROMPT

SQL> set termout off
SQL> set serveroutput on
@awrrpt_all.sql
set termout on
SQL> SQL> SQL> set pagesize 24
SQL> PROMPT AWR reports created.
AWR reports created.
SQL> set serveroutput off
SQL>

thanks,
baskar.l

regards,
baskar.l