In this Document


Purpose

Scope

Details


Enqueue Id1 and Id2 Explanation



Issue analysis




Applies to:

Oracle Server - Enterprise Edition - Version 11.1.0.6 to 11.2.0.3 [Release 11.1 to 11.2]
Information in this document applies to any platform.


Purpose

LOCK: AE "Edition Lock"

Scope

Scope: Local and Global Enqueue.
Deadlock Sensitive: Yes.
Parameters: None

Details

USAGE:
~~~~~~
AE enqueue is used to protect the edition of an object.

The edition of an object is a feature that allows you to upgrade the database component of an application while it is in use, thereby minimizing or eliminating down time. See:

Oracle® Database Advanced Application Developer's Guide
11g Release 2 (11.2)
Part Number E25518-04
Chapter 19 Edition-Based Redefinition
http://docs.oracle.com/cd/E11882_01/appdev.112/e25518/adfns_editions.htm

Edition is a new feature of 11.2, but AE enqueue and some edition related infrastructure was introduced in 11.1

Any session acquires an AE enqueue with share mode (=4) for the edition that a session on.
When a session try to modify or drop edition and requires exclusive access, that session will try to acquire AE enqueue for that edition in exclusive mode (=6).

As an example, most users will see an AE enqueue being held in SHARE (mode 4) for ORA$BASE.

Example:

SQL> select object_id, object_name from dba_objects where object_type='EDITION';

OBJECT_ID OBJECT_NAME
---------- ------------------------------
100 ORA$BASE

SQL> select sid, type, id1, id2, lmode from v$lock where type='AE';

SID TY ID1 ID2 LMODE
---------- -- ---------- ---------- ----------
36 AE 100 0 4
15 AE 100 0 4




Enqueue Id1 and Id2 Explanation


ID1: object id for the edition
ID2: 0





Issue analysis



If you encounter a contention or locking issue where the AE enqueue is prominent, then you need to identify the sessions involved and determine:
•Why the waiter is requesting the AE enqueue in this particular mode that causes it to be blocked by the holder.
•What the waiter it trying to do with the Edition?
•Is the waiter's action reasonable at this time?
•Why the holder is holding the AE enqueue in an incompatible (blocking mode) and/or why the duration of the hold is such that it conflicts with others?
•Is the holder's action reasonable at this time?

Note that the contention itself is unlikely to be the root cause of any issue and it is much more likely that some other activity is causing a process to hold a resource for longer than it needs to or to be manipulating the Edition at an inappropriate time.

If an "AE" enqueue is help but is not blocking other sessions then that would not be an issue.