Status code 5407 for oracle rac backup

Hello,

I am trying to backup an oracle rac in a vmware – srm environment. Fully randomly – or I cannot tell the reason – I get 5407 error, although database status is open. After a shutdown – startup in oracle, simptom disappears.

Did anyone faced with similar error?

Environment is NBU 7.6.0.1, vmware is 5.1.0, and ora is 11.2.

Thanks

Andras