Column | Explanation |
Undo Blocks | Represents the total number of undo blocks
consumed. You can use this column to obtain the consumption rate of undo
blocks, and thereby estimate the size of the undo tablespace needed to
handle the workload on your system. |
# TXN | Identifies the total number of transactions executed
within the period. |
Max Qry Len (s) | Identifies the length of the longest query
(in number of seconds) executed in the instance during the period. You
can use this statistic to estimate the proper setting of the
UNDO_RETENTION parameter. |
Max Tx Concurcy | Identifies the highest number of transactions
executed concurrently within the period. |
Snapshot Too Old | Identifies the number of OER errors
occurring within a period. You can use this statistic to decide whether
or not the UNDO_RETENTION parameter is set properly given
the size of the undo tablespace. Lowering the UNDO_RETENTION
value can reduce the occurrence of this error. |
Out of Space | Identifies the number of OER errors reported in
the current instance. If there is a nonzero value in this column, the
current undo tablespace needs more space (in the UNDO_RETENTION
parameter). |
uS | The number of attempts to obtain undo space by stealing
unexpired extents from other transactions. |
uR | The number of unexpired blocks removed from certain undo
segments so they can be used by other transactions. |
uU | The number of unexpired undo blocks reused by transactions. |
eS | The number of attempts to steal expired undo blocks from
other undo segments. |
eR | The number of expired undo blocks stolen from other undo
segments |
eU | The number of expired undo blocks reused within the same
undo segments |