run {
allocate channel d1 type disk format '/backup/01/sing_%d_%s_%p.bus';
allocate channel d2 type disk format '/backup/02/sing_%d_%s_%p.bus';
allocate channel d3 type disk format '/backup/03/sing_%d_%s_%p.bus';
allocate channel d4 type disk format '/backup/04/sing_%d_%s_%p.bus';
setlimit channel d1 kbytes 4000000;
setlimit channel d2 kbytes 4000000;
setlimit channel d3 kbytes 4000000;
setlimit channel d4 kbytes 4000000;
backup as compressed backupset database filesperset 4;
copy current controlfile for standby to '/backup/01/ctl/singprd.ctl';
release channel d1; 
release channel d2;
release channel d3; 
release channel d4;
}