Hello Samid,
For performance issues, you can take step by step approach .
1. Check with users what exactly performance issues they face e.g: few reports are slow , all the transactions hung , do they get dumps , if they face issues during some particular hours or throughout day ?
2. You can monitor performance issues when it is happening. When they complain, at the same time you can monitor Sm66/Sm50 for any long running transactions(sequential read etc.) or any wp getting into PRIV mode(memory issue) ,check if all the work processes are in use (wp bootleneck) ,in this case there wont be free wp for new request , it causes performance.
3. Check all the parameters buffer ,memory parameters etc. ,if they need to be increased .If you have set Zero memory management ,then check above note mentioned by Sriram to set memory parameters optimally.
4. Check Dialog task response time and part of response times in ST03 ->Expert mode . Here you can check for individual app server or total (all app server together) . Check total to get an idea of overall response time and parts of response time .If DB time is more ,issue is with Db ,if load time is more then issue with ABAP program ,I wait time is high,issue with number of process etc.
Also compare response time for all the app server and see if any app server is heavily loaded(high response time) ,can optimize load balancing here
5. Select the timeframe you need to monitor -> go to "transaction profile" ->Standard(select task type "dialog) ,sort by response time, see which transaction/report is on top .Probably that is causing long run . Double click on that transaction ,you can see users which are running this transaction.
6.Go to "Time profile " to check if any particular hour ,response time is high . double click on that hour ,you can see transactions which run during that hour
7. Check for CPU bottleneck in ST06, if USer and system taking high CPU . If currently if you find ,CPU idle % is less that 20-30 ,then check Top CPU processes to check which process is consuming all the CPU
8. For changed new OS /DB ,there might be need to increase few parameters , check SAP notes for the same
9. Check for locks in Sm12 if there are locks from more than a day old
10. Check for failed jobs to see for any error/dumps
11. Check for st22 dumps for any trends on no of particular dump
12 Check for any error message in SM21
13. Check if file system is full on OS
Hope this helps you to find performance issue
Regards,
Archana