To resolve ORA-00018: Maximum Number of Sessions Exceeded, please read the below points with solutions, and you will get out of this ORA-00018.
The Oracle database management system is known for its robustness and reliability, but users may encounter various errors during its operation. One such error is “ORA-00018: Maximum Number of Sessions Exceeded.”
In this article, we will delve into the details of this error, ORA-00018, its causes, and solutions, with some examples.
Understanding ORA-00018 Error
The “ORA-00018: Maximum Number of Sessions Exceeded” error occurs when the Oracle database reaches the predefined limit for concurrent user sessions. Each session represents a connection to the database, and if the maximum allowable number is surpassed, new connections cannot be established.
Causes of ORA-00018 Error
Several factors can contribute to the occurrence of the ORA-00018 error. Here are some common causes:
Inadequate Session Limits: The DBA (Database Administrator) might have set a relatively low limit for the maximum number of sessions, and the database usage has exceeded this limit.
User connections, especially during peak usage hours, can lead to the exhaustion of available sessions.
Poorly Configured Connection Pooling: If connection pooling is not configured optimally, it can lead to the accumulation of unused sessions, preventing new connections.
Resolving ORA-00018 Error
Solution 1: Adjusting Session Limits
To address the “ORA-00018” error, the DBA can adjust the maximum number of sessions allowed in the Oracle database. This can be done using the following.
ALTER SYSTEM SET SESSIONS = new_limit SCOPE=SPFILE;
Replace “new_limit” with the desired maximum number of sessions. After executing this command, the database needs to be restarted for the changes to take effect.
Solution 2: Identifying and Closing Idle Sessions
Idle sessions can contribute to the exhaustion of available connections. The DBA can identify and terminate idle sessions using the following query:
SELECT * FROM V$SESSION WHERE STATUS = ‘INACTIVE’;
Sessions with a status of ‘INACTIVE’ can be safely closed using the following SQL command:
ALTER SYSTEM KILL SESSION ‘sid,serial#’;
Replace ‘sid,serial#’ with the session identifier and serial number obtained from the previous query.
Solution 3: Optimizing Connection Pooling
If the application uses connection pooling, ensure that it is configured optimally. Periodically check for abandoned connections and implement measures to release them.
Example Scenario
Consider a scenario where an Oracle database is configured with a maximum session limit of 100. Due to increased user activity, the system reaches this limit, triggering the “ORA-00018” error.
To address this, the DBA decides to increase the maximum sessions to 150 using the following SQL command:
ALTER SYSTEM SET SESSIONS = 150 SCOPE=SPFILE;
After making this adjustment and restarting the database, users can establish new connections without encountering the “ORA-00018” error.