This morning I woke up to a few alerts from EM about my archiver being hung, similar to the following:
Target type=Database Instance Target name=orcl4 Categories=Fault Message=The archiver hung at time/line number: Fri Sep 09 06:07:22 2016/376. Severity=Critical
I used the DG Broker to stop and then restart log transport.
edit database orcl set state=transport-off;
edit database orcl set state=transport-on;
But the archiver would still get hung. So its off to the alert log to get more clues. I found this in the primary’s alert log:
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TT00: Attempting destination LOG_ARCHIVE_DEST_2 network reconnect (16484) TT00: Destination LOG_ARCHIVE_DEST_2 network reconnect abandoned Fri Sep 09 08:07:40 2016 Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl4/trace/orcl4_tt00_16068.trc: ORA-16484: compatibility setting is too low
The error message seems self explanatory. I have COMPATIBLE set too low. At this point, I remembered that I changed COMPATIBLE in the primary a month ago. I must have forgotten to also change this in the standby. A quick verfication proved my hypothesis. COMPATIBLE is set to 12.1.0.2 in the primary but 11.2.0 in the standby. So there’s my problem. I changed COMPATIBLE in the standby, bounced it and then resumed log transport. Life was fine and everything was fixed.
If you remember right, I said that I changed COMPATIBLE in the primary a month ago. Why was this a problem today and not back then? To know that, you’d have to know the change history for this database. Last night, we released new code to production. Part of the code release was to include a new table that used Oracle 12c’s new IDENTITY column feature. This was the first 12c-only feature we deployed in our code base. The standby was attempting to create the table with the new feature but that operation could not complete because of the improper parameter setting. I’m still a little confused how this affected log transport. I would have expected only log apply to be broken, but this is how it manifested itself.
