Decompression Errors

1. Z_Data_ERROR
2. Z_MEM_ERROR
3. Z_BUFFER_ERROR

Z_DATA_ERROR: This means that the response received by LR as a response to a request cannot be decompressed either due to bad data or data being corrupted on its way. If you are getting very low amount of these kind of error messages, it either means that your load generator is overloaded or you have network issues intermittently which is corrupting the packets or your servers are having some kind of bottlenecks and due to these bottlenecks they are not in position to send the complete file to the client.

Normally by looking at the content length received from the server response over the duration of time for the same request,one can make out if the server is having the any kind of bottlenecks.If content length looks similar across many requests and if LoadRunner has successfully decompressed some requests and some have failed, it means that either your LG’s are overloaded or you are having networks issues which corrupts the data flowing across the wire.

Z_MEM_ERROR: This error is received if for some reasons your LG’s boxes are running low on memory requirements,and due to less amount of memory,LoadRunner is not able to decompress the server response.Monitor your Load Generator boxes for memory usage.

Z_BUFFER_ERROR: This means LR doesn't have enough buffer size to accept response for an request. Check out my previous post which has the solution for this.

Why do we need a dryrun?

Why is a Dryrun?
Before executing any actual test we execute same scripts for a smaller duration of time. This is called as a Dryrun.

Why do we need this?
There are few important reasons why we perform a dryrun before we begin our actual test

• Server warm-up (Usually servers are bounced before starting the test. Its a good practice in fact)
• Checking for transaction failures (script errors or server side issues or application issues)
• To avoid caching issues which might create outliers

Network Buffer

What is Network Buffer?

Network buffer size sets the maximum buffer size that receives HTTP response from the server. 

How does it impact my test?

If the size of response is huge, then the server will send data in chunks. This will be an overhead to the system when multiple Vusers are running. Default size of network buffer is around 12KB. Follow below mentioned steps to increase the size of network buffer.

• On a WIN 7 system, go to C:\Program Files (x86)\HP\LoadRunner\dat
• Open file called "WebAdvancedOpt.txt"
• Go to line which looks something like this "6="T_EDIT_NUM;Web;NetBufSize;Network buffer size; ..."
• By default, 12288 Bytes is the size of network buffer. This can be increased anything less than 32KB