Rman Backup is too slow

Summary:

Full database rman backup is too slow in windows machine. How to find out the bottleneck ?

Content (required):

run{

ALLOCATE CHANNEL d1 DEVICE TYPE DISK;

ALLOCATE CHANNEL d2 DEVICE TYPE DISK;

ALLOCATE CHANNEL d3 DEVICE TYPE DISK;

ALLOCATE CHANNEL d4 DEVICE TYPE DISK;

CONFIGURE DEFAULT DEVICE TYPE TO disk;

CONFIGURE CONTROLFILE AUTOBACKUP ON;

backup current controlfile format 'D:\rman\%d_RMAN_control_%u.bak';

backup as compressed backupset database format 'D:\rman\%d_RMAN_bckup_%u.bak' tag 'DAILY_BACKUP';

release channel d1;

release channel d2;

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):