Sterling Control Center cannot connect to DB2 Data Base at startup time due to an incorrect user and/or password

Symptom

Sterling Control Center startup doesn't complete. Errors found in CC Engine Log, with DEBUG logging activated:

JdbcConfiguration - testing connection for jdbc:db2://
:<port>/ccenter with user id and password.

[main] ERROR JdbcConfiguration - Exception, "com.ibm.db2.jcc.b.SqlException: [ibm][db2][jcc][t4][2013][11249] Connection authorization failure occurred. Reason: User ID or Password invalid.", occured. Using Password :true

[main] DEBUG JdbcConfiguration - testing connection for jdbc:db2://
:<port>//ccenter without user id and password

[main] ERROR JdbcConfiguration - Exception, "com.ibm.db2.jcc.b.SqlException: [ibm][db2][jcc][t4][10205][11234] Null userid is not supported.", occured. Using Password :false

[main] INFO SCCAgent - An error occurred while starting the engine ...

[main] INFO SCCAgent -

com.sterlingcommerce.scc.common.SCCException: CCTR023E Start Service failed. Service: Agent:Name=CCEngineService,Type=0

---> nested javax.management.MBeanException: Exception thrown in operation start

---> nested com.sterlingcommerce.scc.common.SCCException: CSVC001E Initialization failed. Service: ControlCen

---> nested com.sterlingcommerce.scc.common.SCCException: CCTR027E Error Starting Services.

---> nested com.sterlingcommerce.scc.common.SCCException: CCTR023E Start Service failed. Service: System:Name=JDBCService,Type=JDBC

---> nested javax.management.MBeanException: Exception thrown in operation start

---> nested com.sterlingcommerce.scc.common.SCCException: CSVC001E Initialization failed. Service: JDBC Service

---> nested com.sterlingcommerce.scc.common.ServiceConfigurationException: CJDB023E Could not connect to database. Please check the log file detailed error.

[main] ERROR SCCAgent -