My Oracle Support Banner

Troubleshooting Waits for Locks / Enqueues Other than 'TM', 'TX' and 'UL' (Doc ID 1905157.1)

Last updated on JULY 15, 2022

Applies to:

Oracle Database - Enterprise Edition - Version and later
Oracle Database - Personal Edition - Version and later
Oracle Database - Standard Edition - Version and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Information in this document applies to any platform.


This document provides information regarding locks other than the most common TM, TX and UL Enqueues.
For coverage of User Type Locks (TM, TX and UL Enqueues) refer to the information here:

Document 1392319.1 Primary Note: Locks, Enqueues and Deadlocks (ORA-00060)



Intended Audience: All Database Administrators


To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document
 System Enqueues other than TM, TX and UL Enqueues
 BF enqueue: 'enq: BF - contention'
 CF Controlfile Enqueue: 'enq: CF - contention'
 DW enqueue: 'enq: DW - contention'
 DX Distributed Transaction Enqueue: 'enq: DX - contention'
 FB Block Format Enqueue: 'enq: FB - contention'
 HW High Water Enqueue: 'enq: HW - contention'
 JS Job Scheduler Enqueue: 'enq: JS - queue lock'
 PS Parallel Execution Server Process reservation and synchronization enqueue: 'enq: PS - contention'
 RO Fast Object Reuse Enqueue: 'enq: RO - fast object reuse'
 SQ Sequence Cache Enqueue: 'enq: SQ - contention'
 SS Sort Segment Enqueue: 'enq: SS - contention'
 ST Space Transaction Enqueue: 'enq: ST - contention'
 TO Temporary Table Object Enqueue: 'enq: TO - contention'
 TS Temporary Table Object Enqueue: 'enq: TS - contention'
 TT Tablespace Operations Enqueue: 'enq: TT - contention'
 US Undo Segment Enqueue: 'enq: US - contention'

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.