Oracle Server Manager User's Guide

The Library Cache Monitor

The Library Cache Monitor displays statistics about performance of the library cache. The library cache contains shared cursors and is part of the shared pool in the SGA.

The following figure illustrates the left-most columns of the Library Cache Monitor.

Figure 11 - 5. Library Cache Monitor

The Library Cache Monitor is described below:

Name Space Name of the library cache item. Statistics for the following Name Space items reflect activity for SQL statements and PL/SQL blocks:

SQL AREA

TABLE/PROCEDURE

BODY

TRIGGER

Statistics for other Name Space items reflect activity for object definitions Oracle uses for dependency maintenance.
Gets Requests Number of times the system requests handles to library objects belonging to the name space.
Gets Hits Number of times the requested handle is already allocated in the cache.
If the handle is not already allocated, it is a miss. The handle is then allocated and inserted into the cache.
Gets Ratio Number of Gets Hits divided by Gets Requests.
Values close to 1 indicate that most of the handles the system has tried to get were in the cache.
Pins Requests Number of times the system issues pin requests for library objects in the cache to access them.
Pins Hits Number of times the system pinned and accessed objects that were already allocated and initialized in the cache. Otherwise, it is a miss, and the system has to allocate the object in the cache and initialize it.
Pins Ratio Number of Pins Hits divided by Pins Requests.
Values close to 1 indicate that most of the objects the system has tried to pin and access were in the cache.
Reloads Number of times library objects had to be reinitialized and reloaded with data because they had been aged out or invalidated.
Invalidations Number of times that non-persistent library objects, such as shared SQL areas, have been invalidated.

Filters

The following filter is available in the Library Cache Monitor:

Name Space Filter for the type of library cache object. Monitor displays statistics only for those objects in name spaces that match the Name Space filter.

SQL Worksheet Equivalent

To start the Library Cache Monitor from a SQL Worksheet, you can use the following Server Manager commands:

	MONITOR LIBRARYCACHE

	MONITOR LIBRARY

Required Views

To use the Library Cache Monitor, you must have access to:

V$LIBRARYCACHE

	Statistics for other Name Space items reflect activity for object definitions Oracle uses for dependency maintenance.
Gets Requests	Number of times the system requests handles to library objects belonging to the name space.
Gets Hits	Number of times the requested handle is already allocated in the cache.
	If the handle is not already allocated, it is a miss. The handle is then allocated and inserted into the cache.
Gets Ratio	Number of Gets Hits divided by Gets Requests.
	Values close to 1 indicate that most of the handles the system has tried to get were in the cache.
Pins Requests	Number of times the system issues pin requests for library objects in the cache to access them.
Pins Hits	Number of times the system pinned and accessed objects that were already allocated and initialized in the cache. Otherwise, it is a miss, and the system has to allocate the object in the cache and initialize it.
Pins Ratio	Number of Pins Hits divided by Pins Requests.
	Values close to 1 indicate that most of the objects the system has tried to pin and access were in the cache.
Reloads	Number of times library objects had to be reinitialized and reloaded with data because they had been aged out or invalidated.
Invalidations	Number of times that non-persistent library objects, such as shared SQL areas, have been invalidated.