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.
processes=x sessions=x*1.2 transactions=sessions*1.2
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.