Yesterday I’ve come across a small request from a customer.
They were receiving REGULARLY critical alerts in EM12c from some listeners due to error TNS-12508.
- only 10g listeners were affected
- every day, only one occurrence of the error and always at the same time on a named host
- no apparent correlations between times on different hosts
I’ve analyzed the log to see the error.
11-DEC-2013 20:21:22 * 12508
TNS-12508: TNS:listener could not resolve the COMMAND given
WARNING: Subscription for node down event still pending
11-DEC-2013 20:21:24 * (CONNECT_DATA=(CID=(PROGRAM=)(HOST=xxx)(USER=oracle))(COMMAND=status)(ARGUMENTS=64)(SERVICE=LISTENER_10G)(VERSION=169870336)) * status * 0
11-DEC-2013 20:21:26 * log_directory * 0
11-DEC-2013 20:21:27 * trc_directory * 0
11-DEC-2013 20:21:27 * (CONNECT_DATA=(CID=(PROGRAM=)(HOST=xxx)(USER=oracle))(COMMAND=services)(ARGUMENTS=64)(SERVICE=(ADDRESS=(PROTOCOL=TCP)(HOST=xxx)(PORT=1521)))(VERSION=169870336)) * services *
Notice that after the error there are two requests: show log_directory and show trc_directory.
So I’ve supposed that it’s an additional request failing on 10g listeners but not on 11g listeners.
The “help” command of 10g and 11g releases shows that the two releases have some different commands. One of them is “show oracle_home” that has been introduced in 11g.
- First I’ve searched for scheduled scripts (the customer literally have a huge library of scripts run against the databases to automate maintenance tasks)
- Then I’ve asked to the team that manages an automatic discovery tool that feeds the CMDB
- Finally, I’ve come across this note on Metalink that explain the error:
Repetitive TNS-12508 Errors logged for a listener target after upgrade to 126.96.36.199 DB plugin or higher (Doc ID 1596633.1)
I’ve applied the change to the metrics in EM12c to ignore the error for 10g listeners.