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Don Burleson Blog 







Show redo volume for an active DML transaction

Oracle Database Tips by Donald BurlesonJanuary 6, 2015

Question:  How do I measure the amount of redo that is generated by a DML statement?

Answer:  Oracle does not directly record the volume of redo at the transaction level, but STATSPACK and AWR have some details on redo log switch activity (a measure of redo used at the database-level) and also in the instance activity section of the AWR report. 

If you know which tables are affected by which parts of the application, dba_tab_modifications can give insert/update/delete activity on the tables (if the table monitoring option is turned-on (the default).

Also, you can query v$session for the columns used_ublk (number of undo blocks) and used_urec (number of undo records).  These contain the number of undo blocks and undo records that are held by the current transaction.  It's not an exact way to measure the total amount of redo for an update, but it's a window into the number of data block that are dedicated to redo.

Here is a sample query to display the redo records and redo blocks that are associated with an active session:

   v$session     s, 
   v$transaction t 
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