How much Redo log is being generated by a user sesssion?

Question

How can find which user session is creating the highest redolog entries and how much rego log is being generated?

Answer 1

1) Query V$SESS_IO. This view contains the column BLOCK_CHANGES which indicates how much blocks have been changed by the session. High values indicate a session generating lots of redo.
The query you can use is:
SQL> SELECT s.sid, s.serial#, s.username, s.program,
2 i.block_changes
3 FROM v$session s, v$sess_io i
4 WHERE s.sid = i.sid
5 ORDER BY 5 desc, 1, 2, 3, 4;
Run the query multiple times and examine the delta between each occurrence of BLOCK_CHANGES. Large deltas indicate high redo generation by the session.
2) Query V$TRANSACTION. This view contains information about the amount of undo blocks and undo records accessed by the transaction (as found in the USED_UBLK and USED_UREC columns).
The query you can use is:
SQL> SELECT s.sid, s.serial#, s.username, s.program,
2 t.used_ublk, t.used_urec
3 FROM v$session s, v$transaction t
4 WHERE s.taddr = t.addr
5 ORDER BY 5 desc, 6 desc, 1, 2, 3, 4;
Run the query multiple times and examine the delta between each occurrence of USED_UBLK and USED_UREC. Large deltas indicate high redo generation by the session.
You use the first query when you need to check for programs generating lots of redo when these programs activate more than one transaction. The latter query can be used to find out which particular transactions are generating redo.