Resetting the buffers

This is how to reset different buffers in SAP.

•       One can run the following in SAP command field.

•       /$SYNC      – Resets the buffers of the application server

•       /$CUA         – Resets the CUA buffer of the application server

•       /$TAB         – Resets the TABLE buffers of the application server

•       /$NAM        – Resets the nametab buffer of the application server

•       /$DYNP      – Resets the screen buffer of the application server

•       Caution: Resetting of the buffers could change the performance of the entire system.

 

Performance and SAP R/3 Workload Analysis

 

 

Architecture

• To complete the logon process, the presentation server connects with a dispatcher.
• When the user tries to run a transaction, the user’s request comes from the presentation server to the dispatcher and is put into the local wait queue.
• When the dispatcher recognizes that a work process is available, the user’s request is taken from the wait queue and sent to the work process
• When a user is dispatched to a work process, “user context” data – the user’s logon attributes, authorizations, and other relevant information – is transferred from the roll buffer, extended memory, or the roll file into the work process. This transfer (by copying or mapping, as appropriate) of user context data into work process memory is the mechanism known as a “roll in”.  Transaction processing then begins. 
• If data from the database is required to support transaction processing, a request for data is sent to the database interface, which in turn sends a request through the network to retrieve the information from the database.
• When it receives the request, the database searches its shared memory buffers. If the data is found, it is sent back to the work process. If the data is not found, it is loaded from the disk into the shared memory buffers.
• After being located, the data is taken from the shared memory buffers and sent back across the network to the requesting database interface. Transaction processing resumes. 
• Before accessing the database service, the database interface searches for the data in the R/3 buffers. If the data is found, it is relayed back to the work process where processing resumes. If the data is not found, the database interface sends a request over the network to retrieve the information from the database 
• If the data loaded from the database is eligible for R/3 buffering, it is placed in the R/3 buffers. Transaction processing resumes. 
• When transaction processing is completed, the dispatcher is notified of its completion. The results of the transaction are then sent back to the presentation server. 
• After the transaction finishes and the work process is no longer required, the user context data is rolled out of the work process. 
• CPU time is the amount of time during which a particular work process has active control of the central processing unit (CPU). 
• 
  

 Performance Analysis – Key transaction for Performance monitoring in R/3

Work Process  SM50/SM66
Operating system monitoring  ST06
Workload analysis, use the Workload Monitor (transaction ST03 or ST03N).
Database monitoring ST04
Setup and buffer ST02

Workload time statistics include:

• Response time in milliseconds: Starts when a user request enters the dispatcher queue; ends when the next screen is returned to the user. The response time does not include the time to transfer from the screen to the front end.
• Wait time in milliseconds: This is the time a user request sits in the dispatcher queue. It starts when user request is entered in the dispatcher queue; and ends when the request starts being processed.
• Roll-in time in milliseconds: The amount of time needed to roll user context information into the work process.
• Load time in milliseconds: The time needed to load from the database and generate objects like ABAP source code, CUA, and screen information.
• Processing time: This is equivalent to response time minus the sum of wait time, database request time, load time, roll time, and enqueue time.
• Database request time: Starts when a database request is put through to the database interface; ends when the database interface has delivered the result.
• CPU time in milliseconds: This is the CPU time used by the R/3 work process

If a problem is detected, the data in the Workload Monitor (Transaction ST03N) can be used as follows to identify the area of the system where the problem is located.
First check for general performance problems affecting all transactions. Good general  performance is normally indicated by:

• Wait time < 10% response time
• Main menu (choose Transaction Profile) < 100 ms
• In the Workload Monitor, the following values normally indicate good performance:

• Average roll-in time < 20 ms
• Average roll wait time < 200 ms
• Average load (and generation) time < 10 % of response time (<50 ms)
• Average database request time < 40 % of (response time – wait time)
• Average CPU time < 40 % of (response time – wait time)
• Average CPU time Not much less than processing time

Average  response time – Depends on customer requirements – there is no general rule
Large roll wait time – Communication problem with GUI
Large load time – Program buffer, CUA buffer or screen buffer too small
Large DB time – CPU /mem bottleneck on DB server, Expensive SQL statement, missing indexes, small buffer, missing statistics.

IF wait time >10%
            High database time >40% (response time – wait time) – Analyze database
            Processing time > CPUtime *2 – Analyze hardware
            Load time >50 ms – Analyze R/3 memory config ( program buffer too small)
            Roll in / roll out time >20 ms – Analyze R/3 mem config (extended mem or roll buffer)

 

SAP Performance and Tuning Tools

Any time you must have come across some performance issue with your SAP System, So here i am mentioning some approach that you can follow to avoid the same….

Most Commonly Used Tools and Monitors –AS ABAP
1) Hardware : Application server
OS06 (ST06), OS07
2) Database Gener DBACOCKPIT
DB accesses ST10 ST05, STAD


3) Application :
Shared memory & buffers ST02, SHMM
User memory analysis SM04 S_MEMORY_INSPECTOR
Work process overview SM50, SM66
Workload analysis ST03N STAD
Enqueue monitoring SM12 ST05 4) Communication
HTTP traffic SMICM, ST03G
Remote Function Calls ST03N ST05
Most Commonly Used Tools and Monitors –AS JAVA :
1) Hardware :Application server OS06 (ST06), OS07, SAP MC
2) Database: General DBACOCKPIT, DB02 (Java schema)
DB accesses NWA: Open SQL Monitors, Wily Introscope, SAP JVM Profiler
3) Application: Global Buffers and Caches –> SAP MC, NWA: Open SQL Monitors
JAVA runtime–>Wily Introscope, SAP JVM Profiler
User memory analysis SAP JVM Profiler
Server nodes / thread overview NWA: Operations Management, SAP MC
Workload analysis Wily Introscope
Enqueue monitoring NWA: Open SQL Monitors, SAP MC
4) Communication: HTTP traffic –> HTTPwatch, NWA, SAP MC
Remote Function Calls –> NWA, SAP JVM Profiler, Wily Introscope