Adding to the Pawan information i had noticed the below error in the shared log file,
Caused by: com.pega.pegarules.pub.database.ConnectionException: Database-General problem encountered when reading ruleset versions from the database -4470 [jcc][4.17.29] Invalid operation: Lob is closed. ERRORCODE=-4470, SQLSTATE=null
After doing the small research over this error found an article how to fix this error over here in java stacktrace by using progressiveStreaming=2 for DB2.
So i request you to make sure that you need to add the additional connection parameters which Pega has recommended for the DB2 specific database as follows,
The issue is resolved, by using ":progresssiveLocators=2;progressiveStreaming=2;useJDBC4ColumnNameAndLabelSemantics=2;" for jdbc url along with removing the application username and password in the properties file. Password is not required as we need not connect to the application as RAP is generated directly from the DB.