Dear all,
there is no dataguard standby involved. No Redo Shipping. No DG Broker.
Oracle Support finally came up with a solution:
After increasing redo log files from 512M to 1024M, we no longer see redo
log switches every 4 minutes but only after 50 minutes and the archived
redo logs are no longer only 15-17MB in size but around 180MB. Of course
this is documented neither in the official documentation nor on MOS.
Unfortunately, they could not give a plausible reason for the behaviour.
Another colleague mentioned that the huge 512M granule size could also have
an effect. We are planning to reduce KSM granule size to 128M at the next
maintenance window.
We are also discussing to adapt some other RAC underscores as described in
this Note but have not decided yet: Best Practices and Recommendations for
RAC databases with SGA size over 100GB (Doc ID 1619155.1)
Best regards,
Martin
2017-01-31 17:35 GMT+01:00 Matt Adams <MAdams@xxxxxxxxxx>:
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@xxxxxxxxxxxxx [mailto:oracle-l-bounce@
freelists.org] *On Behalf Of *Martin Decker
*Sent:* Tuesday, January 31, 2017 9:23 AM
*To:* Powell, Mark
*Cc:* oracle-l@xxxxxxxxxxxxx
*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@xxxxxxx>:
What are the values database parameters log_checkpoint_interval and
log_checkpoint_timeout?
------------------------------
*From:* oracle-l-bounce@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> on
behalf of Martin Decker <martin.decker@xxxxxxxxxxxxxxxxx>
*Sent:* Tuesday, January 31, 2017 8:05:55 AM
*To:* oracle-l@xxxxxxxxxxxxx
*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
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
--
--
Martin Decker
Oracle 10g/11g/12c Certified Master
+43 (0) 699 1131 6463 <+43%20699%2011316463>
martin.decker@xxxxxxxxxxxxxxxxx
http://www.ora-solutions.net
--
--
[image: Image removed by sender.]
Martin Decker
Dipl.-Ing. (FH)
Oracle 10g/11g/12c Certified Master
+43 (0) 699 1131 6463 <+43%20699%2011316463>
martin.decker@xxxxxxxxxxxxxxxxx
http://www.ora-solutions.net
[image: Image removed by sender.]
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