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

From: Martin Decker <martin.decker_at_ora-solutions.net>
Date: Tue, 31 Jan 2017 14:05:55 +0100
Message-ID: <CABKFteLA1bMQYUEMfVDnbtnmHPZ2jKdQNtD=UNJArCydUFWt8g_at_mail.gmail.com>



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
Oracle Support SR is open, but so far no clues.

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

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

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Received on Tue Jan 31 2017 - 14:05:55 CET

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