RE: Time duration for which active redolog becomes inactive
- From: D'Hooge Freek <Freek.DHooge@xxxxxxxxx>
- To: "nileshkum@xxxxxxxxx" <nileshkum@xxxxxxxxx>, ORACLE-L <oracle-l@xxxxxxxxxxxxx>
- Date: Sun, 31 May 2009 10:06:41 +0200
Khajwania,
A logfile group stays active as long as it contains the change vectors for
modified blocks that are still in the buffer cache.
These modified blocks are written to the datafiles by the database writer
(dbwr) process.
When a log switch occurs, a checkpoint is triggered in the background, which
will ask the dbwr process to write out the modified blocks that are protected
by the past redo log ( and the latest scn is written to the controlfiles and
datafiles). This is called checkpointing.
This checkpoint is done by oracle in a "lazy" mode, so it could take some time
before the modified blocks are written to disk (also depending on the workload).
Note that modified blocks can already have been written to disk before a
logswitch occurs.
For instance when there are space constraints on the buffer cache, but there
are also parameters (log_checkpoint_interval, log_checkpoint_timeout and
fast_start_mttr_target) which control how aggressive dirty blocks are written
to disk.
A checkpoint can also be forced by executing: "alter system checkpoint".
After this you will see that your active redo log group directly becomes
inactive.
regards,
Freek D'Hooge
Uptime
Oracle Database Administrator
e-mail: freek.dhooge@xxxxxxxxx<mailto:freek.dhooge@xxxxxxxxx>
tel. +32 (0)3 451 23 82
http://www.uptime.be<http://www.uptime.be/>
disclaimer<http://www.uptime.be/disclaimer.html>
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx [oracle-l-bounce@xxxxxxxxxxxxx] On Behalf
Of nilesh kumar [nileshkum@xxxxxxxxx]
Sent: 30 May 2009 20:23
To: ORACLE-L
Subject: Time duration for which active redolog becomes inactive
Hello Everyone,
Good Morning!!
Hope Everyone is doing gr8!!
I have a question in my mind regarding status of redologs.
What is the time duration for which the active redolog group becomes Inactive ?
I know about the logswitch which changes the status of the redolog group. If a
group is Inactive performing the log switches it will change the status of
inactive to current,then further to Active. And if you keep performing switches
it will not chage the status to Inactive but it keep changing from current to
active. What will be the time duration for which It stays Active and then
becomes Inactive does it depends on any parameter in the DB or some thing else.
Please advise.
Thanks
Khajwania
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