Restore fails with ORA-19870,ORA-19587,ORA-27091,ORA-27067

Problem Symptoms
From the backuppiece restore spfile commnad fails with ORA-19870,ORA-19587,ORA-27091,ORA-27067
RMAN> restore spfile from '/backup1/snap/june/8rji9vrq_1_1';

Starting restore at 27-AUG-08
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=36 devtype=DISK

channel ORA_DISK_1: autobackup found: /backup1/snap/june/8rji9vrq_1_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 08/27/2008 01:05:07
ORA-19870: error reading backup piece /backup1/snap/june/8rji9vrq_1_1
ORA-19587: error occurred reading 0 bytes at block number 1
ORA-27091: unable to queue I/O
ORA-27067: size of I/O buffer is invalid
Additional information: 2

Cause of the Problem
RMAN could not read the backuppiece. There may be several reasons behind it. Either it is not the file what is expected in the RMAN command. Suppose my command was restore spfile and this backuppiece may be backups of archived logs. Another reason may be the file in OS level is made read only status. As RMAN opens the backuppiece in read write mode so error may come.

Solution of the Problem
1)Be sure the command you are using is valid one in terms of backuppiece. Suppose here I used restore spfile then this piece must be backup of controlfile.

2)Make sure that backuppiece is read write mode on OS. You can check it on unix by,
$ls -l backupiece_name
In order to make read write mode.
$chmod 666 backupiece_name