11g dataguard broken after primary ran out of space I have Data Guard setup with Primary (A) and read-only standby (B).

primary server (A) ran out of space on the data mount point as auto extend was turned on. I managed to revive it by adding additional files to tablespace on another mount point (there were existing data files on here already, looks like it was added at some point as a stop-gap to give db more space). There are matching mount points on (B) with some other data files there already. The StandbyFileManagement is set to auto.

The standby was erroring with ORA-16766: Redo Apply is stopped.
I ran the following on the standby:

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE OPEN READ ONLY;


Got the following error:

ORA-10458: standby database requires recovery;
ORA-01157: cannot identify/lock data file 71 - see DBWR trace file
ORA-01111: name for data file 71 is unknown - rename to correct file
ORA-01110: data file 71: '/u00/oracle/product/11.2.0/db_2/dbs/UNNAMED00071'


Could someone suggest what the best way to recover from this would be? is it easier just to recover by re-initalizing Data Guard? how would I do that?
Why would you re-initalize everything just because 1 datafile is missing?

On the primary database, create a backup of the datafile:

rman target /
backup datafile 71 format '/tmp/whatever.bkp';


Copy the backup to the standby, then use it:

rman target /
catalog start with '/tmp/whatever.bkp';
run
{
  set newname for datafile 71 to '/path/to/datafiles/whatever.dbf';
  restore datafile 71;
  switch datafile 71 to copy;
}


Then try again.