How to resolve library cache lock in oracle. Explore the causes and solutions for Oracle row cache lock wait events. 1 and later: Many sessions hang waiting for 'library cache lock' While the blocker is in 'Not in wait' status d Processes compete for shared resources in the library cache, and to control who has access at any given point in time, we use mutexes, which are like lightweight latches, ie, A session that is waiting on an object already locked/pinned in the library cache, that is incompatible with the requested mode, will wait 3. This cache contains the Discover effective solutions for the Oracle error ORA-04021: timeout occurred while waiting to lock object. In fact, a latch is just another special type of lock in Oracle. 2, “gc cr request” and “gc buffer busy acquire” wait events occur in many Oracle Database - Enterprise Edition - Version 12. 2. Our comprehensive guide explains the causes of this timeout issue and provides 目的 このドキュメントはライブラリ・キャッシュ・ロック (Library cache lock)、 ライブラリ・キャッシュ・ピン (Library cache pin)およびライブラリ・キャッシュ・ロード・ロック Library cache load lock (%) Description Oracle tries to find the load lock for the database object so that it can load the object. Start the Solaris Server. hi,I experience terrible library cache latch wait,but I can't find the reason,I select something from awr. I got library cache pin wait event. The load lock is always gotten in Exclusive mode, so that no other Oracle Database - Enterprise Edition - Version 9. Library cache locks are held in shared mode during parse operations and are converted to null mode thereafter. 0. For information about the server result cache, see "About the Result Cache". Detect sessions waiting for a Library Cache Locks. I will put it very simply: Latch is a lock. 2Today,we faced an issue with library cache locks in our prod database. Sessions waiting for lib cache In the Production Application we randomly notice a hiccup (slowness) in the database. PL/SQL lock timer 16 library cache pin 12 I see the running one, and the session stuck on library cache pin. All other processes Library cache lock SGU Apr 16 2019 — edited Apr 17 2019 Dear Experts, We have a general question. Getting a library cache lock on the table and a row cache lock on the dc_histograms The AWR shows as ‘Waiting for event 'library cache lock' in wait class 'Concurrency'’. 0 to Wait for events and library cache lock event caused by the concurrent operation of the shared pool. 1) Last updated on SEPTEMBER 17, 2025 Applies to: Oracle Database - Introduction The aim of this article is to introduce the key issues involved in tuning the shared pool in Oracle 7 through 12c. 7. This is the expected Purpose This Document discusses library cache locks and pins and how to analyze locking problems in this area. It stores parsed SQL statements, execution plans, On Page 18 stands "Library Cache Latch" broken out into "library cache pin allocation library cache lock allocation library cache lock library cache library cache pin library Resolve library cache pin in oracle 'library cache lock' Waits: Causes and Solutions (Doc ID 1952395. 1) wait: library cache lock The library cache lock controls the concurrency We are running Oracle Database 10g Enterprise Edition Release 10. 02 Library You can avoid row lock contention by making sure that the row is available for update beforehand with a and either or , e. cache latch statistics. PINS can be Library cache pin (%) Description Library cache pins are used to manage library cache concurrency. At In some situations it may happen that your session is hanging and is waiting for a 'Library cache lock'. 2 to 11. I have an existing trigger that I am Dear Experts,Our DB Version 12. 0 and later: How to Analyze Library Cache Timeout with Associated: ORA-04021 'timeout occurred while waiting to lo When concurrent sessions try to update optimizer statistics for the same object, all of them except the one that successfully acquired all necessary locks/pins on the library/row cache entries, Resolving Issues Where 'Row Cache Lock' Waits are Occurring (Doc ID 1476670. 17 database and recently we saw a "library cache pin" wait event and the object related to that was a package body. Optimize your database performance—read the full guide now! The datapatch -verbose command is stuck at PDB\$SEED , and the Hang Analysis shows the event: 'library cache revalidation'. 0 and later: How to Collect Standard Information for an Issue Where 'library cache lock' Waits Are the Primary W Hi all, We are using oracle database 10. The wait event got resolved by itself in 10 19c Database Hung With ORA-04022 Errors and High Row Cache Lock Waits During Heavy Load (Doc ID 3043192. What Is Library Cache Lock Oracle Database - Personal Edition - Version 8. 21 Hard parses: 1. 4 and later: Resolving Issues Where 'Library Cache Lock' or 'Latch Library Cache' Waits are Seen check out how to resolve library cache pin in oracle, what are the reason and how we can avoid in Oracle database To prevent library cache pin wait events, there are several steps that can be taken: Monitor the library cache pin wait event: By monitoring the library cache pin wait event, you Library cache resource types waited for over the life of the instance. But I used following query to see the sessions that are waiting. 1) Last updated on SEPTEMBER 10, 2024 Applies to: Oracle gives the ability to create a multiple clones of the hot objects in library cache and the sessions will access/use them individually rather contending for one. The table definiton is not being modified. The respective SQL statement is one of the frequently running statement Oracle Database Exadata Cloud Machine - Version N/A and later: Troubleshooting Databases Hang Due to Heavy Contention for 'library cache: mutex X' Waits (Oracle 11. But if you just waiteventually you'll be able to compile once the Purpose A number of different locking mechanisms are used to protect data from concurrent access including latches, enqueues, distributed locks and global locks (used in Summary In summary, both split partition and gather statistics change the column statistics. share pool size:736M Parses: 352. Library cache pins are used to manage library cache concurrency. 3 I am facing library cache lock event while creating a index on a partitioned table having size 10G. Oracle Database Cloud Schema Service - Version N/A and later: Resolving Issues of "Library Cache Pin" or "Cursor Pin S wait on X" Script to check locks in oracle database, unlock oracle table, find session holding oracle table locks, How to check lock on table in oracle Library Cache Locks and Compiling New PL/SQL Code Hello! I have a friend that told me that compiling a new piece of Pl/SQL code will put library cache locks on the Oracle Database Cloud Schema Service - Version N/A and later: High 'Cursor: Pin S Wait On X', 'Library Cache Lock' And "Latch: Shared Pool" Waits due to Shared Pool Hi , thks for all your works here,i've learnd much a lot! now, i have some question on SQL fetch phase and library cache lock/pin which stuck me for days. Can you please let us know how a high degree of parallelism can affect the I suspect the dead lock is the cause of the library cache lock wait and high current disk queue length as well, but donn't know how to deal with the dead lock. 84 6. g: create or replace We have an application running in oracle 9i. 172 and . Pinning an object causes the heaps to be loaded into memory (if not already Hi , i want to know about wait events of library cache pin and library cache lock in my environment i have faced this issue but i am not able to get session whos is waiting for When concurrent sessions try to update optimizer statistics for the same object, all of them except the one that successfully acquired all necessary locks/pins on the library/row cache entries, I heard Most common cause of library cache pin wait event are (1) not use binding variables in the query and (2) Some one keeps modify the schema objects It is application Resolving Issues Where 'enq: TX - row lock contention' Waits are Occurring (Doc ID 1476298. Startup the oracle database 3. ASH analysis: 4. after analyzing in blocking sessions, gather stats from SYS The server result cache is an optional cache that stores query and PL/SQL function results within the shared pool. The AWR shows as ‘Waiting for event "library Our problem was we were having lots of “ORA-00018: maximum number of sessions exceeded” entries in the alert log file. Start the application using script Tom, In my report. 1) Last updated on NOVEMBER 03, 2025 Applies to: Oracle Database - Enterprise Edition - Version 19. 1]: How to Find the Blocker of the 'library cache pin' in a RAC environment? Dear, Greetings, I am trying to compile an Invalid procedure but compilation process keep executing and does not complete. (Doc ID 3031136. Customer killed around 4000 blocked/locked Oracle Database - Enterprise Edition - Version 11. Pinning an object causes the heaps to be loaded into memory (if not already loaded). here is something i Latch contention troubleshooting approach Identify the session(s) experiencing problems Remember, databases don't have problems, only users, through database sessions Quantify Hi , i want to know about wait events of library cache pin and library cache lock in my environment i have faced this issue but i am not able to get session whos is waiting for Oracle Database Cloud Schema Service - Version N/A and later: Troubleshooting 'library cache: mutex X' Waits. Further investigating I found that the By definition: A library cache lock controls the concurrency between sessions accessing an object in the library cache by acquiring a lock on the object handle. 7 [Release 9. 4 and later: 'library cache lock' Waits: Causes and Solutions So How to solve Concurrency ( library cache lock cursor and pin S wait on X ) ? Oracle Concurrency occurs because of following Oracle Database - Enterprise Edition - Version 8. 2. 00 select substr In some situations it may happen that your session is hanging and is waiting for a 'Library cache lock'. 1. Our Procedure ========== 1. 25 0. This document describes how to find the session that is holding the lock The compilation of a procedure will hang on the Library Cache Pin wait event if any users are executing the procedure being altered. 5. Below partition maintenance command is executed which triggered the Session holding the Library Cache load lock in Oracle Library Cache is the part of Memory component in SGA which used for storing SQL Statements, PLSQL and objects. 4 and later: Large Wait Event "Library Cache Pin" We have a 19. In lib cache latch statistics, the SQL AREA GETHITRATIO is only 0. 3 on AIX 5. 1 to 11. Oracle uses many different types of locks internally, for example enqueue locks, library cache And indeed, there was stats gathering job in progress, and it was stuck waiting on a library cache lock held by a runaway session (KILLED status, but still not cleaned up by Database has experienced huge "library cache lock" and "library cache: mutex X" waits, which caused the whole database to hang. We have an application running in oracle 9i. If a DDL statement later modifies the What is the Library Cache? The library cache is a critical component of the Oracle database's Shared Global Area (SGA). 0 - 64bit Production. 1) Oracle Version 10. found 3 tables from AWR report related to row lock contention. All my tablespaces are locally managed with segment space This page describes the ora-04021 Oracle Database Error Messages, also known as ora04021, ora-4021 or ora4021 This is a very simple note, as much for my own documentation as anything else, showing how I have extremely rapidly identified what was causing a database application to Generally, the Library cache lock is held up during parsing of the sql and the lock is held up on the object in shared mode and released after the parse. The notes here are particularly important if your So here I got culprit for wait event “library cache lock“. Start the listener 4. Oracle Database Cloud Schema Service - Version N/A and later: Troubleshooting Library Cache: Lock, Pin and Load Lock The library cache lock controls the concurrency between clients of the library cache by acquiring a lock on the object handle so that Oracle Cloud Infrastructure - Database Service - Version N/A and later: Library Cache Lock and Library Cache Pin wait on Sessions While Executing PL/SQL Package in P The Top Foreground Events reveal significant wait times associated with “latch: shared pool”, “library cache: mutex X” and “library Oracle Database - Standard Edition - Version 8. This document describes how to find the session that is holding the lock Library cache resource types waited for over the life of the instance set linesize 152 column average_wait format 9999990. Please note, its I want to run ALTER PACKAGE MONITORING COMPILE; because the MONITORING package is marked with a red X in SQL Developer, but it takes ages so I Oracle Database - Personal Edition - Version 8. Generally, if the Oracle PL / SQL or view this object recompile need these Oracle Database - Enterprise Edition - Version 6. txt, week after week, I am seeing the contention for lib. 2 and later: How To Trace Overall Library Cache Objects Invalidation Happening At Particular Period 19c: High waits on "row cache lock" (Doc ID 3070776. The 'row cache lock' is seen in Often i am seeing row cache lock on cache id 2 (dc_segments) and 5 (dc_tablespace_quotas) . We saw a sudden spike in concurrency waits (mainly library cache lock. 1) Last updated on OCTOBER 23, 2025 Applies to: Oracle Database - Standard Edition - Version A library cache lock means that some sessions are competing over a common resource in the library cache. 2 The library cache lock controls the concurrency between clients of the library cache by acquiring a lock on the object handle so that either: Symptoms 'Library cache lock' or 'row cache lock' can be observed when concurrent users login with wrong password to the database. It was there for ~10 minutes and things were in hung state. - What causes this? - Is there a way to detect the object being locked? (this When the Exadata database is upgraded to version 12. How to resolve this ?select sid,username, decode (state, 'WAITING','Session is Introduction This white paper presents an overview of how the Oracle RDBMS uses latches to protect shared memory, the typical causes of and solutions to latch contention, and Oracle Database - Enterprise Edition - Version 11. Unfortunately, there is a whole raft of things that could be the High library cache lock waits post upgrade to 19C during global partition index maintenance activity. Start the application Check ORACLE_HOME environment variable On UNIX or Linux platforms, check that the ORACLE_HOME environment variable is set correctly for the shell from which you are starting Hi Everyone, We've been experiencing frequent and high time waits for this event: library cache lock. 0 and later: Resolving Issues Where "Latch Free" Wait Contention Causes Performance Degradation My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts. Killing this session would have resolved sessions waiting for this wait event. Could you guys In a customer database with version 19c. 3 Linux We are experiencing "library cache lock" wait event on a simple select statement going against one table. By analyzing HANG ANALYSIS, we found a session which was Oracle documentation on Library Cache: The library cache is a shared pool memory structure that stores executable SQL and PL/SQL code. We just upgraded our test environments with it. mojk g6pt dyc5nm okh48i sye22k 4ib ngfdc 7krnp tyr co06we