RMAN incremental backup

RMAN> connect target *
run
{
allocate channel t1 type disk format
'/u01/OraApps/oracle/product/11.5.10.2/rman_backup/%d_%s_%t.bak';
allocate channel t2 type disk format
'/u01/OraApps/oracle/product/11.5.10.2/rman_backup/%d_%s_%t.bak';
allocate channel t3 type disk format
'/u01/OraApps/oracle/product/11.5.10.2/rman_backup/%d_%s_%t.bak';
backup incremental level 1 skip inaccessible
TAG='INCREMENTAL_LEVEL_1' database include current controlfile;
release channel t1;
release channel t2;
release channel t3;
allocate channel t1 type disk format
'/u01/OraApps/oracle/product/11.5.10.2/rman_backup/al_%d_%p_%u_%t';
sql 'alter system archive log current';
change archivelog all crosscheck;
backup skip inaccessible archivelog all delete input;
crosscheck backup;
delete obsolete;
delete expired backup;
delete expired archivelog all;
release channel t1;
}