What does the "DBO - Session Summary Total Limit" rule measure? (4377853)

What does the "DBO - Session Summary Total Limit" rule measure?

The Total Sessions Limit shows the percentage of the total session limit being used in the Oracle database. 

This alarm fires when the number of sessions currently connected to the database is about to exceed the value defined in the init.ora parameter file. Upon reaching the number of currently connected sessions, the database will refuse new connections, which can result in an application failure. 

In Oracle12C and higher versions this alarm can also be invoked at the PDB level.

The rule uses the following registry values are thresholds

• DBO_Sess_Sum_Total_Limit_Low for the Warning alarm
• DBO_Sess_Sum_Total_Limit_Medium for the Critical alarm
• DBO_Sess_Sum_Total_Limit_High for the Fatal alarm

To calculate the alarm result

1. It is calculated by taking the sum of active, inactive, killed, cached, and sniped sessions and dividing it by the configured Sessions parameter, which represents the maximum number of sessions allowed.
2. The result is then multiplied by 100 to convert the ratio into a percentage.

Example

Let’s assume the following values:

• Active Sessions = 30
• Inactive Sessions = 10
• Killed Sessions = 5
• Cached Sessions = 3
• Sniped Sessions = 2

Thus, the total number of sessions would be 50

If the maximum allowed sessions is 200, the formula would be 100 * 50 / 200 = 25. This means that 25% of the allowed session limit is currently being used.

If DBO_Sess_Sum_Total_Limit_Low were set to 20, then the Warning alarm should be fired.