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Master Note: Locks, Enqueues and Deadlocks (Doc ID 1392319.1)

Last updated on MARCH 12, 2021

Applies to:

Oracle Database - Personal Edition - Version and later
Oracle Database - Enterprise Edition - Version and later
Oracle Database - Standard Edition - Version and later
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Information in this document applies to any platform.


This document provides an overview reference to content that pertains to the resolution of locks, enqueues and deadlocks affecting the database.

Whole Database "Locking up" or Hanging

If the whole database is "Locking up" or Hanging then this typically is not cause by lock contention and needs to be handled differently. If the database encounters what looks like a hang or a spin conditions refer to the following:

<Document 452358.1> How to Collect Diagnostics for Database Hanging Issues


Questions and Answers

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In this Document
 Whole Database "Locking up" or Hanging
Questions and Answers
 General Notes on Enqueues
 What is an enqueue?
 User Type Locks (TM, TX and UL Enqueues)
 TX Transaction Enqueue
 TM - DML (Table Manipulation) Enqueue
 UL - User Defined Lock
 System Enqueues
 Scripts to help Diagnose Locking Issues
 Deadlocks (ORA-00060)
 What is a deadlock?
 Community Discussions

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