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This article mainly introduces how to do ORA-12520 errors in oracle, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian take you to understand.

ORA-12520: TNS: the listener cannot find an available handler for the requested server type

Listening log is too large; memory is exhausted; os process is exhausted; CPU is too busy; connection storm; shared pool memory is shrinking. Will lead to this situation.

According to the online information:

When you encounter an ORA-12520 error, it looks like this:

English:

ORA-12520: TNS:listener could not find available handler for requested type of server

English:

ORA-12520: TNS: the listener cannot find an available handler for the requested server type

Generally speaking, you should consider the following two aspects:

1: the database is a dedicated server, but the connection method set in the tnsname.ora configuration file is shared, which requires modification of the tnsname.ora configuration file, which usually occurs when you connect to the database server for the first time.

As shown below, after you turn off the shared server configuration of the database server, and then use PL/SQL Developer to connect to the database, an ORA-12520 error occurs.

Alter system set shared_servers=0 scope=both

System altered.

2: when a normal database server suddenly reports an ORA-12520 error, it is usually caused by insufficient process. You need to increase the value of the processes parameter.

However, after checking that both the server and client are in dedicated mode, and the process parameters are sufficient.

Then looking at the monitoring log, we found that it reached 4G, and the phenomenon began on the 1st, while the failure to write in the monitoring log was from the 31st of last month, which is basically consistent with the phenomenon, which may be caused by the excessive size of the monitoring log.

Resolve:

The oracle listener log file is too large to be updated

Resolve the steps:

Lsnrctl set log_status off # # stop the log status first, so that the listener log will not be written

You can back up the listener log files to mv or delete rm now.

Lsnrctl set log_status on # # reopen the log and start recording the listener log. The file is automatically created

You can execute lsnrctl status and check the listener log file

Remember: you cannot directly cat / dev/null > listener_testdb1.log unless the listener is turned off.

Otherwise, the listener cannot write to the log even if the file has been emptied.

You can also specify the name of the listener log file without the system-generated file name:

= =

How to determine whether the connection mode of the oracle database is private or shared

This problem is related not only to the parameters shared_servers and dispatchers, but also to the TNSname.ora files of the server and the client.

The shared_servers parameter on the DB side controls whether server can accept share server connections, but client can force the use of DEDICATED by setting it in TNSname.ora

There are four situations as follows:

DB shared_servers = 0, TNSname.ora server=shared or do not set = > DEDICATED connection

DB shared_servers = 0, TNSname.ora server=DEDICATED = = > DEDICATED connection

DB shared_servers > 0, TNSname.ora server=DEDICATED = = > DEDICATED connection

DB shared_servers > 0, TNSname.ora server=shared or do not set = = > Shared connection

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