RAC & Failsafe :: Archive Logs Are Missing In Hot Backup

We are using the following commands to take hot backup of our RAC database. Hot backup is fired by "backup" user on Linux system.

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rman target / nocatalog <<EOF
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '$backup_dir/$date/%F';
run {
allocate channel oem_backup_disk1 type disk format '$backup_dir/$date/%U';
#--Switch archive logs for all threads
[code]......
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Due to which after command (used 2 times) "sql 'alter system archive log current';" I see the following lines in alert log 2 times. Because of this all the online logs are not getting archived (Missing 2 logs per day), the backup taken is unusable when restoring. I am worried about this. I there any to avoid this situation.
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Errors in file /u01/oracle/admin/rac/udump/rac1_ora_3546.trc:
ORA-19504: failed to create file "+DATA/rac/1_32309_632680691.dbf"
ORA-17502: ksfdcre:4 Failed to create file +DATA/rac/1_32309_632680691.dbf
ORA-15055: unable to connect to ASM instance
ORA-01031: insufficient privileges
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