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Check manual page of oracle_undostat

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Oracle Instance: Undo Retention

Distribution: official part of Check_MK
License: GPL
Supported Agents: Linux, AIX, HP/UX, SOLARIS

This check monitors the Undo Retention in the current Database Instance. The Undo information is very important in Oracle for read consistency of SQL statements. In older time, there was no real monitoring of Undo information and most users did only a monitoring of the Undo Tablespace where that data is placed. Oracle introduced with 9i a new parameter called undo_retention. The value describes the amount in seconds of data that should be hold in the undo Tablespace.

The v$undostat has a column 'tuned_retention' which displays the current number of seconds of Undo data availibe for read consistency. This value could be monitored with this check.

The other important counter is nonspaceerrorcnt which counts the number of 'out of space' events in the Undo Tablespace due to big amount of needed data from current active transactions.

Normaly the checks goes to CRITICAL when a space error occurs. After ~ 10 minutes the counter is resetted back to 0 and the state is OK again. The state for this event could be configured with nospaceerrcnt_state. There is no real usable value for the minimum amount of space errors.

This check needs the Checkmk mk_oracle-plugin installed in the agent. Please refer to the online documentation for how to install that plugin.


The SID of the database in uppercase (as appearing in the process name of the pmon_... process).


One service is created for each running database.