SAP transaction ST06 is an operating system monitor used to review SAP server/system capacity and current utilization of capacity as well as some capacity utilization history. Resource areas monitored by SAP ST06 are CPU, Memory, Swap, Disc and Network of a SAP system. This post would cover following topics related to SAP ST06 operating system/monitor:
- How to run SAP operation system monitor and navigate through important ST06 screens
- How to understand information provided by SAP ST06 screens
1 How to run SAP operation system monitor and navigate through important ST06 screens
1.1 How to start SAP operating system monitor
To start SAP operating system monitor, you can either use menu path , run sap transaction ST06 directly. Please be noted information showed is for the SAP server where ST06 is executed. If your SAP system has more several physical servers and you would like to monitor the server other than what you are signed in, you can display another server status via SM51( run SM51, place cursor on the server, use to menu GOTO->Monitor) or via SAP transaction OS07 (run OS07, then click the server you select).
After you execute SAP transaction ST06, the 1st ST06 screen is the main screen of operating system monitor which has 5 sections-
Figure 1 Part 1 of 2 SAP ST06 Main screen
Figure 2 Part 2 of 2 SAP ST06 Main screen
1.2 how to navigate to other important ST06 screens
SAP ST06 main screen is showing SAP physical server level resource information. There are other ST06 screens which are providing details information or history information you might need for your performance analysis. ST06 provides two ways for you to navigate to ST06 details screen from the ST06 main screen (see above figure-1).
You can use following menu path to navigate to ST06 detail screens:
Or you can click on button “details analysis menu” button from St06 main screen. It would show all options visually.
Figure 3 ST06 – Detail Analysis Menu screen
I personally prefer “Details Analysis menu” since it is more straightforward. Details Analysis menu screen organizes information into 4 sections: current data, hourly history for previous 24 hrs, daily average for last 30 days and additional functions. Based on your analysis need, you can click corresponding button to see more details. For example, if you click on “Top CPU” button, the display would be changed and showing CPU expensive processes at that moment:
Figure 4 ST06 – top CPU processes
2 How to understand information provided by ST06
2.1 how to understand information in ST06 Main screen
Please refer to figure 1 and figure 2 for SAP ST06 Main screen. The main screen layout is organized into five sections. At the top of ST06 screen, it shows date time when the snap-shot is taken and interval (10 sec) which snap-shot is updated by OS collector. Within that interval, the display would not be changed even you refresh the screen. The normal interval is 10 sec which should be good enough.
2.1.1 CPU utilization status in ST06 main screen
This section shows CPU utilization status of a SAP server when ST06 is executed/refreshed.
Explanation on fields in CPU section:
|Utilization||Showing how much CPU is utilized in %. The busy usage consists of user utilization and system utilization. 100% – (user % + system %) = idle % which is % of CPU power available for additional load and function.
Depends on your ST06 or OS collector version, you might see IO wait field % in addition to user, system and idle fields. In this case, the CPU idle rate %= 100% – (user % + system %). In another word, IO wait % is % of CPU power which can be considered “available”.
CPU power consumed by all type of SAP work processes, database processes, ux level scripts etc are counted towards user %. CPU power consumed by Operating system like kernel operation, system interrupts etc is normally counted towards to system %.
SAP recommended CPU idle rate for a server is >=20%. System % should be less than 20%. IO wait % in SAP application server should be less than 10%. IO wait % is normally higher than application server. You need to observe your system to establish baseline on what is accepted threshold for your system. Also, you need to have a right understanding on the 20% idle rate recommendation – this does not say Idle rate in ST06 should be always higher than 20%. It could be normal that there is CPU spike at some moment like busy usage is over 90%. Normally, we measure average idle rate in hourly basis.
In above chart, CPU user utilization is 31%, System is 1% and idle rate is 68% (100% – 31% – 1%).
|System calls/s||Number of system calls per seconds I have not encountered a case which made those fields like system calls, context switches and interrupts fields significant during my performance analysis. You might need to review this if system CPU % is abnormal.|
|Interrupts/s||Number of system interrupts per seconds.|
|Count||Number of processors/CPUs in the physical server.|
|Load Average||Average number of tasks/jobs which is ready for processing but waiting for availabilities of CPU/processors.|
2.1.2 Memory utilization status in ST06 main screen
This section shows available physical memory and utilization when ST06 is executed/refreshed.
Fields explanation in ST06 memory section:
|Physical Mem avail Kb||Showing total physical memory which a server has in KB unit.|
|Physical Mem Free||Showing free memory which is not utilized by any tasks in KB unit.|
|Paged in/s||Average number of pages loaded into memory per second.|
|KB paged in/s||Average size of paged-in in KB per second.|
|Pages out/s||Average number of pages swapped out to disk per second.|
Normally, in a well configured system, number of paging is not critical to performance. At least, i have not encountered a situation where it is a problem.
2.1.3 Swap status showed in ST06 main screen
This section shows swap space configuration and utilization of swap-space when ST06 is executed/refreshed.
Fields explanation in ST06 Swap space section:
|Configured Swap KB||Configured SWAP space in the system.|
|Maximum Swap-space KB||Maximum allowable SWAP space.|
|Free in Swap-space KB||Configured swap space – free in swap-space = occupied swap-space.|
|Actual Swap-space KB||Number of processors/CPUs in the physical server.|
2.1.4 Disc utilization showed in ST06 main screen
This section shows the most busy hard disc when ST06 is executed/refreshed.
Fields explanation in ST06 Disc section:
|Utilization||% of Total IO load on the disc.|
|Avg wait time ms||Average wait time for the disc.|
|KB tansfered/s||Amount of data transferred between Disc and OS|
|Response time ms||Average IO response time for the disc = service time + wait time.|
|Queue||Number of processes waiting for I/O operations.|
|Avg service time ms||Average service time used by the IO subsystem.|
|Operations /s||Number of IO operation per seconds in the past interval( 10 seconds).|
2.1.5 LAN status in ST06 main screen
This section shows LAN traffic status when ST06 is executed/refreshed.
|Packets in/s||Number of data packets received by the server per seconds.|
|Packets out/s||Number of data packets sent by the server per seconds.|
|Collisions||Number of collisions.|
|Error in/s & Errors out/s||Number of data packets in error during receiving and sending process.|
2.2 How to understand information in ST06 details screens
Here, I would explain several of ST06 screens which is important based on my experience in following sections. All screens explained can be accessed from “Details Analysis Menu” screen (see Figure – 3).
2.2.1 Snapshot – TOP CPU process
Click “Top CPU” button in Snap-shot sections, SAP ST06 would display who is using CPU in the latest interval. Please refer to Figure 4 for the display layout.
|Process ID||This is a process id managed by operating system. This is the same process ID showed in SAP transaction SM50/SM66 for a SAP work process. If corresponding process is a database process, you can use SAP transaction ST04 – database monitor to find the corresponding SAP work process if the database process is a shadow process for a SAP work process.|
|User||OS level user under which process is running. This is not a SAP account/user which can be seen in SM50/SM66 etc.|
|Process Name||Process name DW.* is a SAP work process. “*” stands for the instance name. You do not see “*” but instance name in ST06 Top CPU process list screen.
If you run ST06 on a database server, Top CPU process can be a database process. Database process in Top CPU process list can be identified by their brand name like “ORA” for “Oracle” database process. Other processes could be external process. “External” means process which is not related to SAP system.
|Utilization||% of CPU utilization by the process.|
|CPU time||Total time so far for the process since it is started.|
2.2.2 Snapshot – CPU
Click “CPU” button, SAP ST06 would display CPU utilization at individual CPU/Processor level.
Please refer to 2.1.1 section for column explanation. CPU is ID of CPU in the system.
2.2.3 Snapshot – File system
Click “FileSys ” button, SAP ST06 would display file system space configuration and utilization information
|File system name||This is the name manage and recognized by operating system commands like UX command “DIR” etc.|
|Cap. MB||Total disc space for the file system|
|Free MB and Free %||Non-occupied disc space.|
2.2.4 Previous 24 hours – CPU history
Click “CPU” button in Previous 24 hours section, you would have following display showing hourly average utilization.
Please refer to previous section(2.1.1 etc) for column explanation.
2.2.5 Past 24 hours – Memory history
Click “CPU” button in Previous 24 hours section, you would have following display showing hourly average utilization
|MinFree KB||Minimum free memory during the corresponding hour.|
|MaxFree KB||Maximum free memory during the corresponding hour.|
|AvgFree Mem KB||Average Free memory during the corresponding hour.|
2.2.6 Daily average – across servers
Click “across servers” in Daily average section of “Detail Analysis Menu” screen, SAP ST06 would display following screens to show you CPU utilization on a daily average basis.
You can use buttons “Previous Day” and “Next Day” to see daily average for different day.
2.2.7 OS collector
Click “Operating system collector” button, ST06 would display following screen to allow you to start/stop OS collector etc.
3 Further information
Depends on your system version, In your system, you might have SAP transaction OS07 or OS07N. The difference between SAP transaction OS07/OS07N and ST06 is that ST06 only display information from the SAP server/instance where ST06 is executed. OS07/OS07N would display a list of servers which a SAP system has and can display information from any server which you select. You can access operating system monitor via SAP transaction SM51 as well.
Up to now, you have known how to run ST06, navigate through important ST06 screens and understand information in those screens. You might wonder what SAP ST06 can do for performance analysis and trouble shooting. I would cover this in my next post.