To call the buffer monitor:
Choose the following path in the SAP Easy Access menu: Administration →CCMS →Control/Monitoring →Performance →Setup/Buffers →Buffers, or call transaction ST02.
The buffer monitor displays information about buffer and memory usage for the instance where the user is logged on. Statistics are compiled from the time the server is started.
The Tune Summary screen is divided into four parts:
Buffer
The first column shows the names of the buffers:
See also:
Repository Buffer (Nametab Buffer)
Hit Ratio
The hit ratios are displayed as percentages.
A hit is when an object (such as a table, screen, or program) in the buffer is accessed. If the object has to be read from the database, the buffer access fails.
Buffer hit ratio = buffer object reads/logical requests
Buffer Quality
Buffer Quality = saved database calls / (database calls + saved database calls)
The database interface can translate one logical request into several database calls.
Allocated Size
The allocated size is measured in KB. It is different from the available buffer size because a part of the size is used for buffer management.
Freespace
Freespace is important for analyzing the buffer size. The space remaining in the buffer is displayed in KB and percentage of the available buffer size.
Number of Directories
Even though there is freespace in the buffer, objects may not always be loaded into the buffer because there are no more free directories. The Buffers Monitor displays the number of directories available for the buffer, and the number and percentage free. The buffer directories point to the location of the objects that are located in the buffer.
Swapping
When a buffer has insufficient freespace or free directories, it has to swap objects out of the buffer in order to load a new object. The column Swap shows how many objects have been swapped out since system startup.
Database Accesses
When an object cannot be read from the buffer, the database has to be accessed. The number of database accesses is displayed in the last column of this screen.
If a critical situation occurs in a buffer, the data for that buffer (freespace/object swaps) is displayed in red.
SAP Memory
The following information is displayed:
See also:
For more information:
If you require detailed information on an individual memory area, select a line.
In the Detailed Analysis windows (Extended Memory and Heap Memory) include functions that provide information about:
Memory allocation (sequence, size)
Extended memory user
The instance profile settings for memory management
Memory usage over the course of several days.
SAP Cursor Cache
The SAP system has a cursor cache that stores cursors for SELECT statements to avoid time consuming PREPARE processing.
Call Statistics
The Tune Summary screen displays the access statistics for all data either residing in the SAP pool buffers or the database.
The following table describes the information of the tune summary.
Table: Tune Summary
Screen |
Information |
First column |
Contains the different kinds of statements that can be used to access a table. (SELECT SINGLE, SELECT, INSERT, UPDATE, DELETE). |
Last line |
Shows the total - or in the case of the hit ratios, the average - data of the call statistics. |
Next column |
Shows the hit ratios for the SELECT statements for buffered tables. A hit ratio for the other statements (UPDATE, INSERT, and DELETE) is not displayed because these statements always have to be passed to the database. |
ABAP Processor |
Displays the number of logical requests to the buffered tables, and how many of them failed. |
The subsequent columns display:
Table access failures are not the same as buffer access fails. The SQL statements SELECT SINGLE, INSERT, DELETE, and UPDATE can fail if the specified data record does not exist. A buffer access can "fail" if the table has not yet been loaded into the buffer.
Some of the logical requests cannot be satisfied by buffer access, and cause database accesses.
Buffer History
Analyze the buffer history to find the correct buffer sizes.
To display the buffer history:
Choose the following path in the SAP Easy Access menu: Administration → CCMS → Control/Monitoring → Performance → Setup/Buffers → Buffers → Goto → Performance database → This server history.
The data displayed is similar to the columns in the Tune Summary.
The capacities of the buffers may be appropriate for the current system situation. However, you can see that the capacity was too small for recent days. You should resize the buffers even if the situation is not so bad at the moment.
See also: