How to identify when a table is locked in an Oracle database?

In Oracle database, table being locked is a common situation. How to identify and solve this problem is one of the challenges that database administrators often face. This article will introduce how to identify table locks in Oracle databases, and give specific code examples to help database administrators quickly locate and solve table lock problems.

1. How to identify when the table is locked?

1. View the V$LOCK view
The V$LOCK view is an important view used to view lock information in the Oracle database. We can query the V$LOCK view to view the lock information existing in the current database, including lock type, holder session ID, locked objects, etc. The following is a simple query example:

SELECT * FROM V$LOCK WHERE TYPE = 'TM';

This SQL statement will query all table-level lock information in the current database.

2. View the DBA_BLOCKERS and DBA_WAITERS views
The DBA_BLOCKERS and DBA_WAITERS views are views used to view lock conflicts that exist in the database. The DBA_BLOCKERS view displays the objects locked by the current session ID, while the DBA_WAITERS view displays the session IDs currently waiting for lock release. Through the query of these two views, we can clearly understand which sessions are blocking other sessions or being blocked by other sessions. The following is a simple query example:

SELECT * FROM DBA_BLOCKERS;
SELECT * FROM DBA_WAITERS;

2. Specific code example

An actual code example is given below to help readers better understand how to identify that a table in an Oracle database is locked. Case.

--创建一个表并插入数据
CREATE TABLE test_table (
    id NUMBER PRIMARY KEY,
    name VARCHAR2(50)
);
INSERT INTO test_table VALUES (1, 'Alice');
COMMIT;

--在一个会话中锁定表
START TRANSACTION;
LOCK TABLE test_table IN EXCLUSIVE MODE NOWAIT;

--在另一个会话中查看锁定信息
SELECT * FROM V$LOCK WHERE TYPE = 'TM';
SELECT * FROM DBA_BLOCKERS;
SELECT * FROM DBA_WAITERS;

--在第一个会话中释放锁
COMMIT;

Through the above code examples, we can clearly see how to create tables, insert data, and perform table-level locking operations in Oracle database. By querying the V$LOCK, DBA_BLOCKERS, and DBA_WAITERS views, we can easily view the status of the table being locked and further analyze the locking information. After identifying that the table is locked, we can solve the problem of the table being locked by releasing the lock or terminating the session.

Summary: Identifying tables in Oracle databases that are locked is a common task in database management. By querying V$LOCK, DBA_BLOCKERS and DBA_WAITERS views, as well as specific code examples, it can help database administrators quickly and accurately Locate and solve the problem of table locking to ensure the stable operation of the database system.

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