How to deal with an Oracle database table being locked?

Oracle database table locking is a common problem in database management. You may encounter various locking situations during data operations, such as row-level locks, table-level locks, etc. This article will introduce in detail how to handle locked Oracle database tables and provide relevant code examples.

What is an Oracle database table locked?

When a session operates on a database table, the corresponding lock will be generated in the database. If another session also attempts to operate on the same row or table, the table may be locked. In this case, the session may be blocked and data operations cannot be performed normally.

How to detect that an Oracle database table is locked?

You can use the following SQL statement to detect table locking:

SELECT
    c.owner,
    c.object_name,
    c.object_type,
    b.sid,
    b.serial#,
    b.status,
    b.osuser,
    b.machine
FROM
    v$locked_object a,
    v$session b,
    dba_objects c
WHERE
    b.sid = a.session_id
    AND a.object_id = c.object_id;

Methods to deal with Oracle database tables being locked

1. Find session information related to the locked table
   Use the above SQL statement to find the session-related information that caused the table to be locked, including SID, SERIAL#, OSUSER, MACHINE, etc. This information can be used to determine which session caused the table to be locked.

2. Unlock the locked table
   If you determine which session caused the table to be locked, you can unlock the table through the following SQL statement:

   ALTER SYSTEM KILL SESSION 'SID,SERIAL#';

   Where, SID and SERIAL# are the found information of the session that caused the lock.

3. Exclude reasons for locking the table
   It is necessary to analyze why the table is locked. It may be due to uncommitted transactions for a long time, improper data operations, etc. By analyzing the causes, you can avoid similar situations from happening again.

Example

Assume that table EMPLOYEE is locked and SID=123, SERIAL#=456 is detected, resulting in locking. You can execute the following SQL statement unlocking:

ALTER SYSTEM KILL SESSION '123,456';

Conclusion

In Oracle database management, it is common to encounter table locks, which need to be handled in time to ensure the smooth progress of data operations. By finding the session information related to the locked table, unlocking the locked table, and eliminating the reasons for locking the table, you can effectively handle the situation where the Oracle database table is locked. I hope the methods provided in this article are helpful to you.

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