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V$STREAMS_CAPTURE – Waiting for Dictionary Redo

If you are configuring streams, or in my case Change Data Capture (CDC), you will be familiar with the wait events show in the v$streams_capture Oracle view. Once of these wait events is the “Waiting for Dictionary Redo” event.

This is what is shown while the streams capture process is waiting to receive the dictionary redo information from the source database. You have configured the change source, but as yet no information about that source database has been received.

There are a few reasons why this may have happened.

Firstly, you may not have created the change source properly and used the correct first_scn so the change source was not able to identify the information that it needed to. You can correct this in 1 of 2 ways:

  1. Re-create the change source using the correct first SCN.
  2. Get the correct first_scn by using this query:

        SELECT *
        FROM V$ARCHIVED_LOG
        WHERE dictionary_begin = ‘YES’
        ORDER BY completion_time DESC

Now you can use this to recreate the change source with the proper first_scn value.

Secondly, you have added a 2nd change set which uses an existing change source and the dictionary information has not been looked at in the redo logfiles. You can correct this in two steps:

  1. Find out which archived redo logs should be registered against the database using this query:

SELECT consumer_name, name
FROM DBA_REGISTERED_ARCHIVED_LOG
WHERE dictionary_begin = ‘YES’;

  1. You can now register the archived redo log with the database:

ALTER DATABASE REGISTER LOGICAL
LOGFILE ‘G:\oracle\admn\arch_received\1_12672_655801.arc’
FOR ‘CDC$C_TEST_NOLOG_CHGSET’;

Thirdly, you have not told the primary database that you want to add supplemental logging. There are various levels of logging that you can add, so look this up in the Oracle documentation. In brief, you can have minimal logging, key logging or full logging. This can also be specified at either the table or database level. Without supplemental logging of some sort, Log Miner is unable to operate and mine the logs that it receives.

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Category: Change Data Capture


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