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Oracle Tips by Burleson |
OCP Instructors Guide for
Oracle DBA Certification
Chapter 5 - Oracle Database
Objects
Checkpoint Not Complete
Thread 1 advanced to log sequence 248
Current log# 2 seq# 248 mem# 0: /orant/oradata/logs/redolog2a.log
Thread 1 cannot allocate new log, sequence 249
Checkpoint not complete
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. Oracle will stop processing until the checkpoint completes
successfully.
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. For example, if the database 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. The DBA must
make sure 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.
The above text is
an excerpt from:
OCP Instructors Guide for Oracle DBA Certification
A Study Guide to Advanced Oracle Certified Professional Database
Administration Techniques
ISBN 0-9744355-3-8
by Christopher T. Foot
http://www.rampant-books.com/book_2003_2_OCP_print.htm
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