Undo Statistics 

Definition

This submonitor in the SAP/Oracle Database Monitor lets you check the undo statistics provided by the Oracle view GV$UNDOSTAT. You can see:

·        Daily summaries

·        Undo statistics: daily and average values

·        Maximum space consumption for undo tablespaces

Use

You choose Detailed Analyses ®  Overall activity  ® Undo Statistics and the required tab page Daily Summaries, Undo statistics, or Max space consumption.

You cannot view history information in this monitor.

Structure

Entries marked “RAC only” appear only for Oracle Real Application Cluster (RAC)

·         Daily Summaries

This tab page displays daily summaries of undo statistics:

Column	Description
Instance Id RAC only	Database instance ID
begin date	Begin date for the analysis
begin time	Begin time for the analysis
end date	End date for the analysis
end time	End time for the analysis
last active undo tablespace	Last active undo tablespace
total number of undo blocks	Total number of undo blocks
total number of transactions	Total number of transactions
length of the longest query (sec)	Length of the longest query in seconds
highest Nbr. of TAs executed Concurrently	Highest number of transactions executed concurrently
attempts to obtain undo space	Attempts to obtain undo space
unexpired undo blocks removed	Unexpired undo blocks removed
unexpired undo blocks reused	Unexpired undo blocks reused
attempts to steal expired undo blocks	Attempts to steal expired undo blocks
expired undo blocks stolen from segments	Expired undo blocks stolen from segments
expired undo blocks reused	Expired undo blocks reused
number of occurrences of ORA-01555	Number of occurrences of ORA-01555
nbr of times space was requested	Number of times space was requested
number of transactions per second	Number of transactions per second

Each row in the table shows information for a 10-minute period, as shown by the difference between Begin Time and End Time. The information is derived from the view GV$UNDOSTAT, which also holds information in this way.

You can see information from the previous 7 days, since there are 1008 rows in the view GV$UNDOSTAT.

·         Undo statistics

This tab page displays the same information as above, with individual tab pages for each day.

There is also a Daily statistics tab page showing the statistics – maximum, minimum, average, and total – for each day.

RAC only

The tab page Undo statistics does not appear when you choose DB instances ® Total to show the total of all RAC instances.

 

·         Max Space Consumption

This tab page displays maximum space consumption for undo tablespaces:

Column	Description
Instance Id RAC only	Database instance ID
undo tablespace name	Name of the undo tablespace
total undo tablespace size in MB	Total size of the undo tablespace in MB
max. used undospace in MB	Maximum used undospace in MB
max. used in %	Maximum percentage used undospace