|Oracle® Database Reference
12c Release 1 (12.1)
|PDF · Mobi · ePub|
|Default value||Derived: (1.5 *
|Range of values||1 to 216 (which is 1 to 65536)|
SESSIONS specifies the maximum number of sessions that can be created in the system. Because every login requires a session, this parameter effectively determines the maximum number of concurrent users in the system. You should always set this parameter explicitly to a value equivalent to your estimate of the maximum number of concurrent users, plus the number of background processes, plus approximately 10% for recursive sessions.
Oracle uses the default value of this parameter as its minimum. Values between 1 and the default do not trigger errors, but Oracle ignores them and uses the default instead.
The default values of the
TRANSACTIONS parameters are derived from
SESSIONS. Therefore, if you increase the value of
SESSIONS, you should consider whether to adjust the values of
TRANSACTIONS as well. (Note that
ENQUEUE_RESOURCES is obsolete as of Oracle Database 10g release 2 (10.2).)
In a shared server environment, the value of
PROCESSES can be quite small. Therefore, Oracle recommends that you adjust the value of
SESSIONS to approximately 1.1 * total number of connections.
For a CDB, the root container's
SESSIONS parameter specifies the total number of sessions for the database.
SESSIONS parameter for a PDB specifies the total number of sessions that can be used by that PDB. Its value defaults to the root container's
SESSIONS value. If the PDB tries to use more sessions than configured by its
SESSIONS parameter, an
ORA-00018 error message is generated.
SESSIONS parameter for a PDB can only be modified by the PDB. It cannot be set higher than the CDB's