Oracle Solution for Error ora-01252

ORA-01252: cannot prevent writes - file string in recovery manager backup

What triggered the Error:

An attempt to make a tablespace read only or offline normal found that a recovery manager proxy backup is in progress. If the file is made offline or read-only, then the file header cannot be updated when the backup is complete.

What should we do to fix it:

Wait for the Recovery Manager backup to complete and retry this command.