What process is this?

[Shem_1]

What is does "ora_smon....." doing? Its taking up lots of procesor % Somewhere about 80-99%

[Steven E. Protter · Accepted solution]

1) You can not run your database without it.
2) smon is the monitor process that is supposed to activate very infrequently. It pretty much makes sure the database is running right nothing more.

If its using lots of CPU you have problems with your database or database networking.

You want to look for issues in your alert logs and use tnsping to test network connectivity.

It would be a good idea to tell us your Oracle Version Number and perhaps upload a copy of init.ora for more detailed help.

There should be one smon process per database instance.

How many instances are you running on this machine?

SEP

[Bill Douglass]

SMON is the Oracle system monitor process. It can be rather busy doing a recovery if you start up a database that was not closed down properly.

[Michael Steele_2]

'SMON' is a background process that performs oracle instance recovery at instance startup. Should be an SMON for each instance.

'SMON' has slighty different responsibilities in parallel server.

[malay boy]

well don;t touch smon...Or you Oracle database going to be wacko.

Here are some summaries what SMON do :

1) instance recovery
2) coalesce free space
3) Deallocate temporary segments

regards
mB

[Yogeeraj_1]

hi,

SMON - Temporary Segment Cleanup and Free Space Coalescing in Oracle 7.3 and Higher

Attached a document from metalink that answers all your questions.

hope this helps!

regards
Yogeeraj

[twang]

What is SMON doing?
Once you have identified that SMON is using lots of CPU, you need to identify whether it is performing temporary segment (extent) cleanup, or free space coalescing.

[twang]

I have an experience that SMON background process is running for long time, I try to SHUTDOWN IMMEDIATE the database but hangs.
It seems SMON have to either clean up a large number of temporary extents, or to coalesce
a large number of free extents. This can manifest itself by SMON appearing to
spin, consuming a high percentage of CPU for long periods.
During a SHUTDOWN IMMEDIATE and SHUTDOWN NORMAL, SMON is cleaning up extents
which are no longer needed and marking them as free.
In this case, we either wait for SMON to clean up the free extents in the database as it
shuts down or perform a SHUTDOWN ABORT to shutdown the instance. Eventually we SHUTDOWN ABORT the database, but note that a SHUTDOWN ABORT will not perform a clean shutdown.

[twang]

I have experienced that SMON process is running for long time.
I try to SHUTDOWN IMMEDIATE the database but hangs. It seems SMON have to either clean up a large number of temporary extents, or to coalesce a large number of free extents. This can manifest itself by SMON appearing to spin, consuming a high percentage of CPU for long periods.
During a SHUTDOWN IMMEDIATE and SHUTDOWN NORMAL, SMON is cleaning up extents which are no longer needed and marking them as free.
In this case, we either wait for SMON to clean up the free extents in the database as it shuts down or perform a SHUTDOWN ABORT to shutdown the instance. Eventually we SHUTDOWN ABORT the database, but note that a SHUTDOWN ABORT will not perform a clean shutdown.