Lab128 - Tools for Advanced Oracler Tuning and Monitoring.
Reference Guide.
Transactions and Rollback Segments
The Transactions and Rollback Segments window provides detail about active transactions.
It also lists Rollback segments, shows cumulative statistics, and highlights which segment is used by an active transaction.
Use this window to identify the age of the transaction, how much of redo is generated, number of locked objects etc.
Viewing options.
There are two tabular views in this window: upper one - Transactions; lower one - Rollback Segments.
As a different transaction is selected, the corresponding rollback segment is highlighted.
Below is an example of this window. Also, the picture shows the location of hot spots: the SID and LckObj columns.
Click on these columns to open the Session Details and Lock and Locked Object Details
windows, respectively.
Descriptions of the columns in the Transactions tabular view.
N - Instance ID / Node number (RAC only) (gv$transaction.INST_ID);
SID - Session ID (v$session.SID);
SERIAL# - Session serial number (v$session.SERIAL#);
USERNAME- Session user name (v$session.USERNAME);
START_TIME- Transaction start time (v$transaction.START_TIME);
UBLK- Number of undo blocks used (v$transaction.USED_UBLK);
UREC- Number of undo records used (v$transaction.USED_UREC);
RBS_Name- Rollback segment name (dba_rollback_segs.SEGMENT_NAME);
LckObj - Number of locked objects by the session (count of v$lock.TYPE where TYPE='TM');
Descriptions of the columns in the Rollback Segments tabular view.
USN - Undo/Rollback segment number (v$rollstat.USN);
SEG_NAME - Rollback segment name (dba_rollback_segs.SEGMENT_NAME);
TS_NAME - Session serial number (dba_rollback_segs.TABLESPACE_NAME);
RSSIZE - Size of the rollback segment in bytes (v$rollstat.RSSIZE) - history of changes is also available;
UsedUndo - Used amount of rollback segment in bytes (sum of corresponding v$transaction.USED_UBLK multiplied by corresponding dba_tablespaces.BLOCK_SIZE);
WRITES - Cumulative number of bytes written to the rollback segment (v$rollstat.WRITES) - history of changes is also available;
XACTS - Cumulative number of active transactions (v$rollstat.XACTS) - history of changes is also available;
GETS - Cumulative number of header gets (v$rollstat.GETS) - history of changes is also available;
WAITS - Cumulative number of header waits (v$rollstat.WAITS) - history of changes is also available;
HWMSIZE- High water mark of rollback segment size (v$rollstat.HWMSIZE);
SHRINKS - Cumulative number of times the size of a rollback segment decreases (v$rollstat.SHRINKS) - history of changes is also available;
WRAPS - Cumulative number of times rollback segment is wrapped (v$rollstat.WRAPS) - history of changes is also available;
EXTENDS - Cumulative number of times rollback segment size is extended (v$rollstat.EXTENDS) - history of changes is also available;
