DB password is encrypted and is stored in the mqgroup.ini file, within /nastel/apwmq/config/groups dir.
If you changed your database password, you would need to run a Navigator database utility called nsqsqlmk, located within /nastel/apwmq/bin, in order to update it. Example of nsqsqlmk command:
./nsqsqlmk -DNASTEL_APWMQ -pDNASTEL_PERMITS -pUdbuserid -pPpassword -Udbuserid -Ppassword -mMQM -s4010
Once executed, run options 6 and 7. Exit the utility and start the workgroup server.