Check the paths.

In the script ...
BACKUP INCREMENTAL LEVEL 1 DATABASE
format 'Z:\meera\RMAN\%d_%s_%p.bkp' tag=fullbkp
PLUS ARCHIVELOG
format 'Z:\meera\RMAN\ARC_%d_%s_%p.bkp' tag=arcbkp;
release channel t1;
and RMAN is trying to backup to ...

ORA-19504: failed to create file "Z:\MALKUWARI\RMAN\ARC_QF_8_1.BKP"
ORA-19504: failed to create file "Z:\MALKUWARI\RMAN\ARC_QF_9_1.BKP"
Are you running the correct script?

Thanks,