Analyzing Network Performance Using Network Statistics in the DBA Cockpit

[Karen_Kuck]

Are you unhappy with your system performance and ask yourself:

• Are my long database response times due to long processing times on the database server or slow communication between the database server and the SAP application server?


• How are the network statistics distributed among the Db2 members and the SAP application servers of my system?


• How long is the network time compared to the server time?


• How long is the average network time per roundtrip and how does this metric react to a changing network load?

Did you know you can use the network statistics in the DBA Cockpit to find out?

Here’s how:
Start the DBA Cockpit (transaction DBACOCKPIT) and go to the Network Statistics screen under Performance. It gives you details of the network communication between SAP application server and database.

Let’s have a look at an example of how you can use the Network Statistics screen to analyze your network performance:

In the Selection area, choose a time frame and a few settings for the graphic and for the list view of the statistics.



After applying your selection, you get two graphics: The first one shows the average network time per roundtrip for each application server as line graph, and the bytes sent and received as stacked columns.

The line graphs show the values of the drilldown options that you’ve selected (here: application server), the stacked columns show aggregated values for the entire system.
You can already see that the average network time per roundtrip is quite high.

The second graphic shows the ratio of network time/server time as line graphs, and the absolute values of network and server time as stacked columns. Here you can also see that the values are rather high:



As an alternative to the graphics, there’s also a list view for the network statistics.  Again, you can see that the ratio network time/server time is quite high. We have a ratio of 2.2 here in our example:



Let’s have a closer look and go back to the Selection area to drill down for more details about application server no. 17, which has particularly high values:



You can see something’s wrong here:

• The average network time per roundtrip is consistently high and increases up to 4,000 microseconds.


• With a higher load, the network time per roundtrip increases.


• Network times are far too high compared to server times.

Let’s compare these values to the values of a healthy system:

Here in the healthy system, the network statistics are as you’d expect them to be:

• The average network time per roundtrip in this system remains below 750 microseconds. It’s much lower than the up to 4,000 microseconds in our problem system.


• The graph for the average network time per roundtrip remains relatively stable compared to our problem system where the average network time per roundtrip increased with the workload.


• The ratio of network time to server time varies little, and the ratio is low.

So, in our first example, it’s not the system, it’s really a network issue that would need further investigation now.

Let us know in the comments if...

...you found this blog helpful and if you were able to solve performance problems using the network statistics screen in the DBA Cockpit.

This blog’s content is also available in a video.

[DeepikaSingh]

This is good explaination .

Do we have any soft threshold of whats good and whats not good ?

Also what should be do next if we find high times?

[Frank-Martin]

Hi Deepika,

The answer depends a little on the type of application. A typical SAP ERP system executes a large amount of simple and fast SQL queries where the network time can easily outweigh the database execution time.

You should keep an eye on the ratio (network time/ database time) . If this ratio is larger than 1 the network time becomes more important than database execution time. If the ratio is much larger than 1 , tuning SQL and the database will not give you much performance enhancement. On an ERP system you will typical reach a ratio of one if your average network time is somewhere between 0.5 and 0.7 ms. Average network rountrip times of 1ms or higher is typically too large for a well performing SAP application server.

If the network roundtrip times become too large you should contact your network administrators and check your network settings and throughput . If the network roundtrip times go up at certain times of the day the network may be overloaded during those times. The overload may be caused by other network activities ( e.g. a DB2 backup running using the same network ).

Regards

Frank