Thursday, July 29, 2010

SESSIONS

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Property
Description
Parameter type
Integer
Default value
Derived: (1.1 * PROCESSES) + 5
Modifiable
No
Range of values
1 to 231
Basic
Yes
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 ENQUEUE_RESOURCES and TRANSACTIONS parameters are derived from SESSIONS. Therefore, if you increase the value of SESSIONS, you should consider whether to adjust the values of ENQUEUE_RESOURCES and 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 (Note that ENQUEUE_RESOURCES is obsolete as of Oracle Database 10g release 2 (10.2).)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.

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V$TRANSACTION_ENQUEUE

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V$TRANSACTION_ENQUEUE displays locks owned by transaction state objects.

Column
Datatype
Description
ADDR
RAW(4 | 8)
Address of lock state object
KADDR
RAW(4 | 8)
Address of lock
SID
NUMBER
Identifier for session holding or acquiring the lock
TYPE
VARCHAR2(2)
Type of lock. TX indicates transaction enqueue.
ID1
NUMBER
Lock identifier #1 (depends on type)
ID2
NUMBER
Lock identifier #2 (depends on type)
LMODE
NUMBER
Lock mode in which the session holds the lock:
  • 0 - none
  • 1 - null (NULL)
  • 2 - row-S (SS)
  • 3 - row-X (SX)
  • 4 - share (S)
  • 5 - S/Row-X (SSX)
  • 6 - exclusive (X)
REQUEST
NUMBER
Lock mode in which the process requests the lock:
  • 0 - none
  • 1 - null (NULL)
  • 2 - row-S (SS)
  • 3 - row-X (SX)
  • 4 - share (S)
  • 5 - S/Row-X (SSX)
  • 6 - exclusive (X)
CTIME
NUMBER
Time since current mode was granted
BLOCK
NUMBER
The lock is blocking another lock

Oracle data dictionary views



Last updated: 2009-11-12 Thursday