RE: Log switches every 4 minutes with 17MB Archivelogs despite 500MB log file size

I recall seeing similar issues in the past where DG broker was involved. From what I recall, the log switches were a lot more frequent though.  

Thanks

Ramsankar Cheruvattath (Ram)

407-209-6276

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Matt Adams
Sent: Tuesday, January 31, 2017 11:35 AM To: martin.decker_at_ora-solutions.net; Powell, Mark Cc: oracle-l_at_freelists.org
Subject: RE: Log switches every 4 minutes with 17MB Archivelogs despite 500MB log file size  

That phrase 'MAXIMUM PERFORMANCE' in the log file makes my thing that standby database management might be involved, but I don't think I've ever seen quite this situation before.  

We have standby databases, do not use the Data guard broker.  

Is this rac cluster also the primary for a standby site? Is it possible that the data guard broker software is doing this somehow to force changes from a primary to a standby database?      

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Martin Decker
Sent: Tuesday, January 31, 2017 9:23 AM
To: Powell, Mark
Cc: oracle-l_at_freelists.org
Subject: Re: Log switches every 4 minutes with 17MB Archivelogs despite 500MB log file size  

Dear Mark, Bertrand,

log_checkpoint_interval is not net

log_checkpoint_timeout is not set

archive_lag_target is not set

no cron jobs

no dba_jobs

no dba_scheduler_jobs

"alter system" audit enabled, but no audit records generated in neither audit_file_dest nor dba_audit_trail

fast_start_mttr_target was not set, and is now set to 300s, but does not a difference.

Redo Log Buffer is not specified and defaults to around 500 MB, we have 4 CPU Cores with hyperthreading, so 8 visible cores per host.  

More details (v$log, init.ora contents, x$kcrfstrand) can be found here: https://drive.google.com/file/d/0B_d8Sdgtmy-rUGlIWkFFaWJhYWc/view

Regards,

Martin    

2017-01-31 14:54 GMT+01:00 Powell, Mark <mark.powell2_at_hpe.com>:

What are the values database parameters log_checkpoint_interval and log_checkpoint_timeout?  

From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on behalf of Martin Decker <martin.decker_at_ora-solutions.net> Sent: Tuesday, January 31, 2017 8:05:55 AM To: oracle-l_at_freelists.org
Subject: Log switches every 4 minutes with 17MB Archivelogs despite 500MB log file size  

Dear List,

in a RAC 2 Node cluster (12.1.0.2 with DBBP October 2016), we see redo log switches every 4 minutes with Archivelogs filled up to 15-18 MB. Redo Log File size is 512MB. The Application is using the instances with singleton services so node1 has much more redo generation compared to node2.

It is unclear what is triggering the redo log switches. We can exclude the following:

• ALTER SYSTEM SWITCH LOGFILE;
• ALTER SYSTEM ARCHIVE LOG CURRENT;
• RMAN ARCHIVELOG / DB BACKUP
• ARCHIVE_LAG_TARGET

Any ideas on how to diagnose? LOG_ARCHIVE_TRACE shows that log switch is exectued, but not who/what is triggering the switch:

• 2017-01-19 14:13:58.496248 1380 krsl.c krsl_log_switch_trace: Beginning Log Switch operation for MAXIMUM PERFORMANCE: krsk_ler_get: Read LE 16 flag 0xa T-1.S-888 low 0x000c.d4c16698 nxt 0xffff.ffffffff nab 4294967295 switching from log 16 thread 1 sequence 888 to log 12 thread 1 sequence 889

Best regards,

Martin  

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Martin Decker
Oracle 10g/11g/12c Certified Master
+43 (0) 699 1131 6463 <tel:+43%20699%2011316463> 

martin.decker_at_ora-solutions.net
http://www.ora-solutions.net






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Martin Decker
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Oracle 10g/11g/12c Certified Master

+43 (0) 699 1131 6463

martin.decker_at_ora-solutions.net
http://www.ora-solutions.net

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