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What does the Oracle listener status / services "UNKNOWN" mean?


  • Product: Aleph
  • Product Version: 22, 23
  • Relevant for Installation Type: Dedicated-Direct,Direct,Local,Total Care



What does it mean, if the Oracle listener status (util O / 2 / 4) shows status 'UNKNOWN'?


Service "" has 2 instance(s). 
Instance "aleph22", status UNKNOWN, has 1 handler(s) for this service... 
Instance "aleph22", status READY, has 1 handler(s) for this service... 


Oracle's explanation for the "UNKNOWN" status handler is this - 

"An UNKNOWN status means that the instance is registered statically (with a SID_LIST) in the listener.ora file rather than dynamically with service registration. Therefore, the database status is "not known" to the listener. There is no reason a connection cannot be made, however, using the SID value. 

For normal communication, the SID_LIST in the listener.ora file is not required. One of the reasons why Oracle recommends not using one, is because it may cause un-necessary overheads on the listener process. The SID_LIST section only needs to be used for instances such as PLSExtProc or if older OEM tools are in use. It is not normally a problem having the instance duplicated in the SID_LIST, but it is preferable not to have it." 

We have the SID_LIST configured to specify ORACLE_HOME in listener.ora, like this:



Thus the overhead. But the application should have no problem to connect to the database using SID



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