Hi,
It seems that your oracle_home is not properly mounted. In AIX if you are using directories as mount points then it gives such error if permissions differ for root and ora<sid> on same file system.
Try following:
login with root and execute following command at os level on database server.
1- Shutdown your database
2- uumount /oracle/BMQ/102_64
3- chmod 755 /oracle/BMQ/102_64
4- mount /oracle/BMQ/102_64
After this login with orabmq user and try to execute offline backup of the dataabse.
Regards
Krishan