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Seeing dropped packets in Protocolstats.log and how to reduce them.

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Article ID: 42593

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Updated On:

Products

CA Application Performance Management Agent (APM / Wily / Introscope) INTROSCOPE

Issue/Introduction

 Symptoms: Seeing dropped packets in the protocolstats log.

 

 Environment: APM 9.6 and later TIMs. This does not apply to MTP TIMs. 

 

 Cause: 

 The current APMpacket capture buffer size may be too small. In APM 10.0-10.2, it is configurable through apmpacketsettingsdb property via the configtool. 

 The default value is 20 MB. Note that is far less than the default value in prior releases (CEM 4.x to APM 9.6) which is 60 MB. In 10.3 and later, the 60 MB

 value will be restored. 

 

 Workaround:

 Below are steps to change the capture buffer size's default value:

 1. Go to the correct directory 

 cd /opt/CA/APM/tim 

 

 2. List the current contents on the apmpacketdatabase setting file:  

 bin/configtool -f ../apmpacket/config/apmpacketsettings.db -l

 MaxLogSizeInMB = 1  -- By default the only value set in the settings database

 

 3. Set the capture buffer size to 60. Note that all records in the database are a parameter and the corresponding value.

 bin/configtool -f ../apmpacket/config/apmpacketsettings.db -s CaptureBufferSizeInMB 60

 

 4. Verify that the new configuration setting is included.

 bin/configtool -f ../apmpacket/config/apmpacketsettings.db -l

 CaptureBufferSizeInMB = 60

 MaxLogSizeInMB = 1

 

 Notes: 

 1. You may raise this value even higher if dropped packets do not disappear. Typically going no higher than 250 MB is sufficient. 

 2. After making this change, go to protocolstats and check that the CPU count has not dramatically increased. Too high CPU overhead will be negatively impact the  packet capture needed by the TIM process.

 3. Typically dropped packets are due to too much information being sent to the TIM from the switch. So cleaning up and filtering network traffic to the TIM should be the first action to be investigated.

 

 Additional information:

 A detailed discussion of the APMpacket settings database will shortly be made into a KB.

 

Environment

Release:
Component: CEM