Why the lock concept is introduced
What is a lock
The management and allocation of all Oracle 9i locks is done automatically by the database management system, which does not require user intervention, but also provides manual locking commands for experienced users.
Classification of Locks
1. Divide by permissions
Exclusive lock
Shared locks
2. Division of resources by lock allocation
Data lock
Dictionary lock
Query Lock Information
(1) The database lock interface as shown in Figure 6.71.
(2) in the "Filter" Drop-down list box shown in the figure, you can choose the type of display lock, including 3 types, default to user type lock.
Table 6.6 Key information for locks
Name |
Meaning |
User name |
Oracle UserID associated with a session that occupies or acquires a lock |
Session ID |
session that occupies or acquires a lock |
Lock type |
The type of user lock or system lock. User application Gets the user type lock. Any process that blocks other users may occupy one of these locks. User type locks include 3 kinds. TM (DML team), TX (transaction queue) and UL (User provided) |
Manner of occupancy |
How locks are locked by the session |
Way to request |
How the process requests locks to be locked |
Object Name |
Lock the name of an object |
Limit of ROWID |
Locked Current ROWID |
Object owner |
User name of object owner |
Object type |
Object type |
Resource ID1 |
Lock identifier #1 (depending on type) |
Resource ID2 |
Lock identifier #2 (depending on type) |