dba_apply_dml_handlers

SELECT APPLY_NAME, PRECOMMIT_HANDLER,
DECODE(APPLY_CAPTURED, 'YES', 'Captured', 'NO', 'User-Enqueued')
APPLY_CAPTURED
FROM DBA_APPLY
WHERE PRECOMMIT_HANDLER IS NOT NULL
/

dba_apply_enqueue

This view displays information about the Apply enqueue actions for all the rules in the database.

dba_apply_error

This view displays information about error transactions generated by the Apply processes in the database. This is a very useful view to keep track of the errors generated by the Apply process. This view should be queried as often as possible to see if there are any errors. In case error rows show up in this view, the DBA should immediately begin further investigation of the errors and rectify them.

Some useful columns include:

• LOCAL_TRANSACTION_ID shows the local transaction ID for the error transaction whereas the SOURCE_TRANSACTION_ID shows original transaction ID at the source database.
   

• MESSAGE_COUNT is useful as it shows the total number of events inside the error transaction.
   

• SOURCE_COMMIT_SCN displays the original commit SCN for the transaction at the source database.

As an example, the following SQL statement shows details of Apply Error Transactions: