Go to Transaction ST03 and identify the Transaction, User and Process which are consuming more than the threshold values.
We can schedule a report in background to collect the values into ST03
The reports are displayed differently for Expert Mode, Administrative Mode and Service Engineer
R/3 Buffers
Buffering: The frequently accessed content and rarely changed content is stored as buffer in the application server which is also referred as R/3 buffers.
R/3 Buffers: These are stored in the instance and cannot be shared between the Instances. These buffers are different from database buffers. There are various types of buffers.
Ex: Program Buffers, table Buffers, Calendar, CUA, Screens etc…. Buffers are stored in the shared memory of the instance.
Buffer Mechanism: User logs into the system to access certain data. The request is processed and goes to database to fetch the content. If the content is eligible for buffering it is stored in the instance.
The content should be rolled out into user context before the response is sent to the user. As the user context is small in size the context I not stored in user context. But in terms store in R/3 buffers and the pointer to R/3 buffers are stored in user buffers.
Note: User context cannot be shared between users but R/3 buffers are shared between users.
Buffer Monitoring: Buffers are monitored in ST02. Buffers are organized in terms of directories and the space in the memory.
ST02: Display the following information 1. Name of the Buffer context
2. Buffer hit ration: The ration should be always greater than 94% 3. SWAPS
We need to look for swaps. Swaps occurs when the allowed space is completely used or of all the directories used or both utilized.
Basically the ABAP buffer size will be 150 MB by default. We can increase up to 600 MB (Up to 4 times) based on the available memory.
If swaps occur frequently consider increasing either space or directories.
1. Frequent transaction of objects 2. The new modules are implemented 3. Buffer memory is not sufficient 4. Number of directories not sufficient 5. Frequent changes to the buffer data
Note: In each company the swaps occurs frequently but look into the number of swaps. Based on the size of the database we can allow 5000 to 25000 swaps. They are not effecting the performance of the system i.e. response time. Double click on the context which has more swaps.
Click on parameters to identify the parameter name and value and to change in RZ10 before changing any parameter read type. Complete documentation in RZ11. Miss configuration or improper configuration may not start the SAP engine.
TABLE Buffering: Apart from the repository objects SAP also buffers the table content based on the table data (content).
There are 4 types o buffering:
1. No Buffering: The table which is large frequently updated rarely accessed is set to no buffering.
2. Full Buffering: (100 % Buffering) The table which is small, frequently accessed and rarely changed is eligible for full buffering
3. Single Record Buffering: The table which is relatively large but frequently accessed is buffered using primary key
4. Generic Key Buffering: The buffering is based on group of keys Note: For most of the tables SAP define the buffering settings, which can be modified in SE13.
BY default SAP provides the following options for buffering tables. 1. Buffering Allowed: This tale can be buffered
2. Buffering Allowed but Switched off: This is used for development and quality systems
Exercise: List out at least 5 tables in each of 7 cases. SE13 and SE14
Buffer Synchronization:
1. When more than one instance is configured we need to synchronize the data between buffers of the instances. If not we will get the old snapshot.
2. When data is fetched by one instance it will keep a log in the table DDLOG
3. Even the content is accessed from buffers it will check the dialog always
If there is a difference in time stamp it will fetch the data from database. Mean while we can synchronize the data between instances using the following two parameters:
rdisp/buffertime= 60 sec: This parameter will refresh buffers every 60 seconds
rdisp/buffermode= send on execute/ send off execute. Due to performance reasons use send off, If only one instance is configured.
End User End User End USer DB CI R/3 Buffers DI R/3 Buffers DI R/3 Buffers
Memory
It’s a temporary work area to perform calculations, Reads the data from the disk. No operations are allowed on the hard disk without memory.
1. Physical Memory : The amount of memory that is installed on the system is called as physical memory.
2. Virtual Memory : As the physical memory is not enough we need to assign space on the disk which is referred as page file. This memory is referred as virtual Memory.
SAP Memory Management:
SAP recommends using Zero memory management so that memory automatically managed.
Memory Assignment:
When a user is assigned with work process the work process requires memory to roll the user information.
In order to roll the user information from ROLL AREA (U.C) into Task Handler work process requires memory.
Each work process assigned with a memory called Roll Memory which is defined by parameter ztta/roll_area= 2 MB.
By default it is 2 MB, and this is the maximum memory a user can use. But initially when the user request we will assign around 1 MB that is specified by parameter ztta/roll_fiorst= 1 MB