What is a library cache lock?
This lock is also obtained to locate an object in the library cache. Library cache lock will be obtained on database objects referenced during parsing or compiling of SQL or PL/SQL statements (table, view, procedure, function, package, package body, trigger, index, cluster, synonym). The lock will be released at the end of the parse or compilation.
What is the purpose of this event in the cache?
This event controls the concurrency between clients of the library cache. It acquires a lock on the object handle so that either: One client can prevent other clients from accessing the same object. The client can maintain a dependency for a long time (for example, so that no other client can change the object).
What is the use of concurrency in a library cache?
This is used to control concurrency between clients of the library cache by acquiring a lock on the object handle. Uses are (b)The client can maintain a dependency for a long time (no other client can change the object).
How much of the DTIME is the event library cache lock?
Analyzing the AWR we can verify that 89% of the DTIME of the database in the contention period was the event library cache lock.
What percentage of the DTIME of the database in the contention period was the event library cache lock?
When is the library lock released?
Why do I like to work in troubleshooting?
Why does a client acquire a lock on the object handle?
Do pipes use a SQL lock?
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How do you find the session holding a library cache lock?
Open the tracefile and do a search for "PROCESS
How do I resolve library cache pin wait event?
The library cache pin wait event is associated with library cache concurrency. It occurs when the session tries to pin an object in the library cache to modify or examine it. The session must acquire a pin to make sure that the object is not updated by other sessions at the same time.
What is the use of library cache?
The library cache stores the executable (parsed or compiled) form of recently referenced SQL and PL/SQL code. The data dictionary cache stores data referenced from the data dictionary. The server result cache is an optional cache that stores query and PL/SQL function results within the shared pool.
What is library cache hit?
This metric represents the library cache efficiency, as measured by the percentage of times the fully parsed or compiled representation of PL/SQL blocks and SQL statements are already in memory.
What is concurrency wait event in Oracle?
Concurrency. Waits for internal database resources (for example, latches) Configuration. Waits caused by inadequate configuration of database or instance resources (for example, undersized log file sizes, shared pool size) Idle.
What is latch shared pool?
Latch: shared pool (%) This latch protects the allocation of memory from the shared pool. If there is contention on this latch, it is often an indication that the shared pool is fragmented.
What is a library cache?
The library cache is not one cache, but many. It contains the pseudo code for PL/SQL program units. It contains parse trees and execution plans for shareable SQL statements. It also contains abstract representations in a form called DIANA of the database objects referenced by the SQL statements.
What is stored in library cache in Oracle?
The library cache includes the shared SQL areas, private SQL areas (in the case of a shared server configuration), PL/SQL procedures and packages, and control structures such as locks and library cache handles.
What is library cache and data dictionary cache?
One area is called the data dictionary cache, also known as the row cache because it holds data as rows instead of buffers (which hold entire blocks of data). The other area in memory to hold dictionary data is the library cache.
What is library cache miss?
What is a library cache miss, and how do I correct it? Answer: A library cache miss is correlated to a "hard parse", a case where the SQL must be loaded into the shared pool. Anytime a session issues SQL statement that does not already exist in the shared pool, then Oracle has to do a hard parse.
What is a cache hit Oracle?
The Buffer Cache Hit Ratio Oracle metric monitors the rate at which Oracle finds the data blocks it needs in memory over the lifetime of an instance. Also see: Using the data buffer advisory utility.
What is shared pool?
The shared pool is the area of the System Global Area (SGA) that contains structures such as the data dictionary cache and the shared SQL area. This is one of the most important storage structures in an Oracle database system.
What is the use of library cache contains user information such as user privileges used to store shared SQL log of changes made to the database all of the above?
The Library Cache is a piece of memory within the SGA that Oracle uses in order to store SQL Statements. It is used to store shared SQL.
What is Oracle buffer cache?
The buffer cache is the in-memory area of the SGA where incoming Oracle data blocks are kept. On standard Unix databases, the data is read from disk into the Unix buffer where it is then transferred into the Oracle buffer. The size of the buffer cache can have a huge impact on Oracle system performance.
What is Oracle dictionary cache?
Dictionary Cache is the memory areas designated to hold dictionary data. It is also known as the row cache because it holds data as rows instead of buffers (which hold entire blocks of data). When an Oracle database is first started, no data exists in the data dictionary cache.
What is the use of extent in Oracle?
Overview of Extents. An extent is a logical unit of database storage space allocation made up of a number of contiguous data blocks. One or more extents in turn make up a segment. When the existing space in a segment is completely used, Oracle allocates a new extent for the segment.
To check the Library Cache Lock contention | Oracledbwr
Library cache resource types waited for over the life of the instance. set linesize 152 column average_wait format 9999990.00. select substr(e.event, 1, 40) event,
How does one diagnose and fix 'library cache pin' waits?
How does one diagnose and fix 'library cache pin' waits? - LIBRARY CACHE PIN usually occurs during compiling and recompiling PL / SQL, VIEW, TYPES. First we will determine the blocker information as:.....
Library Cache lock in parallelized Statements - Stack Overflow
The only time I can remember a CTAS causing a locking issue was some bugs with extremely high parallel degrees. You might want to check your parameters and see how high PARALLEL will go. It is probably a combination of RAC nodes * cpu_count (parameter) * parallel_threads_per_cpu (parameter).
'library cache lock' Waits: Causes and Solutions - Oracle
Oracle Database - Personal Edition - Version 8.1.7.4 and later: 'library cache lock' Waits: Causes and Solutions
Library Cache Lock -- How to find object from handle address
Oracle Version 10.2.0.3 Linux We are experiencing "library cache lock" wait event on a simple select statement going against one table.
performance tuning - library cache pin and library cache lock - Oracle
performance tuning - library cache pin and library cache lock Hi , i want to know about wait events of library cache pin and library cache lockin my environment i have faced this issue but i am not able to get session whos is waiting for library cache pin and session which is acessing that object .Request to guide me on this , additionally any sc
What percentage of the DTIME of the database in the contention period was the event library cache lock?
Analyzing the AWR we can verify that 89% of the DTIME of the database in the contention period was the event library cache lock.
When is the library lock released?
The lock will be released at the end of the parse or compilation.
Why do I like to work in troubleshooting?
Well, as I have already shown, I like to work in the area of troubleshooting and performance because every incident is a battle and you will never imagine what you will find as a problem and how the case will end. One tip I leave here ... always have good weapons in the battle for it to end quickly.
Why does a client acquire a lock on the object handle?
It acquires a lock on the object handle so that either: One client can prevent other clients from accessing the same object. The client can maintain a dependency for a long time (for example, so that no other client can change the object). This lock is also obtained to locate an object in the library cache.
Do pipes use a SQL lock?
Cursors (SQL and PL/SQL areas), pipes and any other transient objects do not use this lock.
What is the maximum allowed value for KGL_latch_count?
The maximum allowable value for kgl_latch_count is no greater than 66 according to Oracle support per Bug # 1381824. Now move on to learning more about shared pool latches within Oracle.
What is the Oracle latch count?
There is a hidden Oracle database initialization parameter called kgl_latch_count which controls behavior in terms of the number of library cache latches created within the Oracle database . By default, this value should not be changed as it is sufficiently set in most cases. In the event that there should be a library cache contention issue and no other recourse is available to resolve the contention with the library cache latch, this value can be increased.
What percentage of the DTIME of the database in the contention period was the event library cache lock?
Analyzing the AWR we can verify that 89% of the DTIME of the database in the contention period was the event library cache lock.
When is the library lock released?
The lock will be released at the end of the parse or compilation.
Why do I like to work in troubleshooting?
Well, as I have already shown, I like to work in the area of troubleshooting and performance because every incident is a battle and you will never imagine what you will find as a problem and how the case will end. One tip I leave here ... always have good weapons in the battle for it to end quickly.
Why does a client acquire a lock on the object handle?
It acquires a lock on the object handle so that either: One client can prevent other clients from accessing the same object. The client can maintain a dependency for a long time (for example, so that no other client can change the object). This lock is also obtained to locate an object in the library cache.
Do pipes use a SQL lock?
Cursors (SQL and PL/SQL areas), pipes and any other transient objects do not use this lock.