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TNS-12602: TNS: Connection Pooling limit reached


Sometimes You can get “TNS-12602: TNS: Connection Pooling limit reached  ” error.


Details of error are as follows.

TNS-12602: TNS: Connection Pooling limit reached
Cause: The operation failed because maximum active current connections has been reached.
It may not be a real error when the Connection Pooling feature is enabled. It is possible that the application
later reissues the operation and successfully grabs the connection pool slot and proceeds.
Action: This is an internal error. Enable tracing and attempt to repeat the error. If it occurs again,
contact Oracle Customer Support.



To avoid this problem, increase the number of initial dispatchers as follows:

Shutdown the Dispatcher using the following command

SQL> alter system shutdown immediate 'D001';

Later on add new dispatchers as follows:

SQL> alter system set DISPATCHERS = '(protocol=tcp)(dispatchers=10)';

Note : This syntax depends on the way the Dispatcher value is given in the init.ora or Spfile.ora

While increasing the DISPATCHERS value, also check shared servers ratio.

See the documents and notes on Shared Server configuration for these details.


Do you want to learn more details about RMAN, then read the following articles.


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