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Oracle Checkpoint Not Complete Tips

Oracle Database Tips by Donald BurlesonJanuary 14, 2016

Question:  :  I am seeing very slow import utility because of redo.log file errors "Checkpoint cannot complete".   I'm assuming that I need to add redo.log files to accommodate the checkpoint not complete message?  What else can I do to reduce the checkpoint not complete messages in my alert log?

Answer: The "checkpoint not complete" messages are generated because the logs are switching so fast that the checkpoint associated with the log switch isn't complete.   

During that time, Oracle's LGWR process has filled up the other redo log groups and is now waiting for the first checkpoint to successfully execute.   

Remember, Oracle will stop processing until the checkpoint completes successfully!  

Usually you see this "checkpoint not complete" error in your alert log:

Thu Jan 14 22:12:55 2015
Thread 1 cannot allocate new log, sequence 46352
Checkpoint not complete

Oracle suggests that you might consider setting archive_lag_target to zero to reduce "checkpoint not complete" messages:

alter system set archive_lag_target=0 scope=both;

Overall Oracle performance can be dramatically improved by increasing the log sizes so that logs switch at the recommended interval of 15 to 30 minutes.  

Identify the current size of the redo log members from v$log, record the number of log switches per hour and increase the size of the log to allow Oracle to switch at the recommended rate of one switch per 15 to 30 minutes.  

See here, important notes on how to monitor online redo log switches.  

For example, if the database redo log size is 1 megabyte and you are switching logs every 1 minute, you will need to increase the log size to 30 megabytes in size to allow it to switch every 30 minutes.  

The problem is that many applications have workloads that vary dramatically throughout each 24-hour time-period. In addition, application-processing workloads may vary according to the days of the calendar month.  

Month-end and mid-month processing may increase the number of changes occurring in the database. This higher level of activity may cause the redo logs to be filled much more quickly than during off-peak times.  

You need to ensure that the on-line redo logs don't switch too often during periods of high activity and switch often enough during times of low processing workloads.   

This should reduce the delays from the checkpoint not complete errors.

MOSC note 435780.1 has tips on avoiding the checkpoint not complete error:

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