I have this issue with DB links from a readonly standby database.
tried to select from another DB through a link,but it errors with the follwoing message:

ERROR at line 5:
ORA-00372: file 1 cannot be modified at this time
ORA-01110: data file 1: '/exxx_dataxxx/xxxx/system_01.dbf'

This is a database.

The same happens with a 10G R1 instance as well,but the error message is :

ERROR at line 1:
ORA-16000: database open for read-only access

I have verified that the links are created properly.
Is it true that we cant query a remote DB from a readonly DB using DB links?

What could the errors mean?

Thanks in advance.