ORA-00018: maximum number of sessions exceeded


Sometimes you can get ” ORA-00018: maximum number of sessions exceeded ” error.

Details of error are as follows.


 ORA-00018: maximum number of sessions exceeded

Cause: An operation requested a resource that was unavailable.
               The maximum number of sessions is specified by the initialization parameter SESSIONS.
               When this maximum is reached, no more requests are processed.
Action: Try the operation again in a few minutes.
               If this message occurs often, shut down Oracle, increase the SESSIONS parameter in the initialization parameter file, and restart Oracle.
To solve this problem, you need to increase the sessions parameters. Sessions parameters depend on processes and transactions parameters.
So you can increase these 3 parameters according to following formula.
You can change these parameters as follows.
SQL> alter system set processes=1000 scope=spfile;

SQL> alter system set sessions=1200 scope=spfile;

SQL> alter system set transactions=1440 scope=spfile;

SQL> shutdown immediate
SQL> startup
If your existing parameter value was bigger than 1200, you can set it to 2000 or 4000 according to your database environment.


Do you want to learn Oracle Database for Beginners, 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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