ORA-12602: TNS: Connection Pooling limit reached


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


Details of error are as follows.

ORA-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.



About Mehmet Salih Deveci

I am Founder of SysDBASoft IT and IT Tutorial and Certified Expert about Oracle & SQL Server database, Goldengate, Exadata Machine, Oracle Database Appliance administrator with 10+years experience.I have OCA, OCP, OCE RAC Expert Certificates I have worked 100+ Banking, Insurance, Finance, Telco and etc. clients as a Consultant, Insource or Outsource.I have done 200+ Operations in this clients such as Exadata Installation & PoC & Migration & Upgrade, Oracle & SQL Server Database Upgrade, Oracle RAC Installation, SQL Server AlwaysOn Installation, Database Migration, Disaster Recovery, Backup Restore, Performance Tuning, Periodic Healthchecks.I have done 2000+ Table replication with Goldengate or SQL Server Replication tool for DWH Databases in many clients.If you need Oracle DBA, SQL Server DBA, APPS DBA,  Exadata, Goldengate, EBS Consultancy and Training you can send my email adress [email protected].-                                                                                                                                                                                                                                                 -Oracle DBA, SQL Server DBA, APPS DBA,  Exadata, Goldengate, EBS ve linux Danışmanlık ve Eğitim için  [email protected] a mail atabilirsiniz.

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