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Server startup failure, ClassFormatError in PRClassLoaderDB



Sometimes the Pega server fails to start and displays the errors. After several more attempts, the server eventually starts up.

Error Messages

2016-06-08 15:30:48,774 [ vafscmul9376] [ ] [ ] ( etier.impl.EngineStartup) ERROR - PegaRULES initialization failed. Server: unknown PRNodeImpl init failed
at com.pega.pegarules.session.internal.mgmt.PREnvironment.getThreadAndInitialize(
at com.pega.pegarules.session.internal.PRSessionProviderImpl.getThreadAndInitialize(
at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineStartup.initEngine(
at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl._initEngine_privact(
at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl.doStartup(
at com.pega.pegarules.session.internal.engineinterface.etier.ejb.EngineBean.doStartup(
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(
at sun.reflect.DelegatingMethodAccessorImpl.invoke(
at java.lang.reflect.Method.invoke(
Caused by: java.lang.ClassFormatError: Illegal class name "" in class file com/pega/pegarules/exec/internal/util/classloader/PRClassLoaderDB
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(
at com.pega.pegarules.bootstrap.loader.PRAppLoader.findClassInternal(
at com.pega.pegarules.bootstrap.loader.PRAppLoader.findClass(
at com.pega.pegarules.bootstrap.loader.PRAppLoader.loadClass(
at com.pega.pegarules.bootstrap.loader.PRAppLoader.loadClass(
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(
at com.pega.pegarules.session.internal.mgmt.PRNodeImpl.initialize(
at com.pega.pegarules.session.internal.mgmt.PREnvironment.getThreadAndInitialize(
... 113 more
2016-06-08 15:30:48,789 [ vafscmul9376] [ ] [ ] ( etier.impl.EngineStartup) INFO - PegaRULES initialization failed. Server: unknown

Steps to Reproduce

Restart the server.

Root Cause

A defect or configuration issue in the operating environment suggests a problem with the state of the database schema.


Perform the following local-change:
Restore the database schema to a good copy..


Suggest Edit

Published July 25, 2016 - Updated October 8, 2020

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