Support Article

Seeing hung connections



The user recently upgraded from 6.3 to 7.2.1 in their QA environment. They are seeing frequent hung threads related to the db environment that they did not experience in the 6.3 environment. There are hung thread messages in the attached SystemOut.log file.

Error Messages

[1/13/17 21:17:10:317 GMT] 000001c1 AppServerBrid E com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega Problem during method invocation (invokeEngine)
java.lang.NoClassDefFoundError: com/pega/apache/log4j/spi/ThrowableInformation
at com.pega.apache.log4j.spi.LoggingEvent.<init>(
at com.pega.apache.log4j.Category.forcedLog(
at com.pega.apache.log4j.Category.error(

Steps to Reproduce

Happens during normal processing as well as occassionally on jvm recycles

Root Cause

A defect or configuration issue in the operating environment .In the above trace we can see that server is not able to load classes correctly from database.


Set the below DSS setting and restart the server:

Ruleset: Pega-Engine
Purpose: prconfig/initialization/preloadengineclasses/default
Value: com.pega.pegarules.priv.util.StackTracecom.pega.apache.log4j.spi.ThrowableInformation

To set via DSS - refer

The DSS setting is to circumvent this, to forcibly pre-load that class. Even from the thread dump trace we can see that it is looking for the same package.

Published February 14, 2017 - Updated February 18, 2017

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