WebLogic Server does not start

Issue: When you start WebLogic Server instance, the server would not come up and the start script hangs.
Symptoms:
In the /servers/AdminServer/logs/Adminserver.log you would find the following error.
####<Aug 27, 2009 3:47:58 PM EDT> <Critical> <WebLogicServer> <gaalpltapp0040> <AdminServer> <main> <<WLS Kernel>> <> <> <1251402478485> <BEA-000386> <Server subsystem failed. Reason: java.lang.NumberFormatException: null
java.lang.NumberFormatException: null
at java.lang.Integer.parseInt(Integer.java:415)
at java.lang.Integer.parseInt(Integer.java:497)
at weblogic.ldap.EmbeddedLDAP.validateVDEDirectories(EmbeddedLDAP.java:1035)
at weblogic.ldap.EmbeddedLDAP.start(EmbeddedLDAP.java:212)
at weblogic.t3.srvr.SubsystemRequest.run(SubsystemRequest.java:64)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:200)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:172)
>
####<Aug 27, 2009 3:47:58 PM EDT> <Notice> <WebLogicServer> <gaalpltapp0040> <AdminServer> <main> <<WLS Kernel>> <> <> <1251402478508> <BEA-000365> <Server state changed to FAILED>
####<Aug 27, 2009 3:47:58 PM EDT> <Error> <WebLogicServer> <gaalpltapp0040> <AdminServer> <main> <<WLS Kernel>> <> <> <1251402478509> <BEA-000383> <A critical service failed. The server will shut itself down>
####<Aug 27, 2009 3:47:58 PM EDT> <Notice> <WebLogicServer> <gaalpltapp0040> <AdminServer> <main> <<WLS Kernel>> <> <> <1251402478511> <BEA-000365> <Server state changed to FORCE_SHUTTING_DOWN>


Solution:

When you see above error, please check
1. if the disk space is full
2. if disk space is fine, then delete the following file
/servers/AdminServer/data/ldap/conf/replicas.prop
and restart the server. WLS sometimes corrupts the file replicas.prop and is often results in above error