RMAN-06571 after switch database to copy

Question

Hi all,
I rolled forward a physical standby database using RMAN incremental backups as detailed in Oracle support ID **836986*.1* and it all went well until i tried to switch the standby database to copy.
I get the error RMAN-06571 datafile 24 does not have recoverable copy
Now datafile 24 is a datafile created after the scn of the standby database and there's unfortunately no documentation on how to restore this datafile from the backup piece created as part of the incremental backup created from the primary. The oracle document says
*"if any datafiles have been added to primary after scn <n> they will also have to restored to the standby host and cataloged before doing the switch"*
Unfortunately it does not say how this is to be done.
I have tried to restore datafile 24 but even that produces an
RMAN-12008 could not locate backup piece /x/y/piecename
even though the backup piece is in the location /x/y/piecename and has been cataloged via rman. The same backup piece was used to restore the datafiles that existed earlier. i.e. the other 23, successfully so i know it has the datafile i need.
My environment is a 3-node RAC (Primary & Standby). I am really at my wits end.
All help appreciated.

Answer 1

rman> restore datafile 24;
It accurately determines that the datafile to be restored is in the backuppiece /x/y/piecename but then informs me it cannot find it.
RMAN> @restoredatafile24.txt
RMAN> run {
2> allocate channel c1 device type disk format '/opt/dbe/forstandby_%U';
3> restore datafile 24;
4> release channel c1;
5> }
allocated channel: c1
channel c1: SID=1347 instance=rac1 device type=DISK
Starting restore at 19-JUL-2012 22:49:15
released channel: c1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 07/19/2012 22:49:16
RMAN-12009: command aborted because some backup pieces could not be located
RMAN-12008: could not locate backup piece /opt/dbe/forstandby_f0ngb1k4_1_1
RMAN> **end-of-file**
Thanks.
Edited by: user11970290 on Jul 20, 2012 12:53 PM