rman脚本

哪位大师帮忙分析下这个脚本，详细点说明，新手看不懂呢？ORACLE_SID=higfmis1
export ORACLE_SID
rq=`date +"%Y%m%d" `
xx="start time":`date +"%Y%m%d%H%M" `
>/exp/script/higfmis_disk.log
echo $xx>>/exp/script/higfmis_disk.log
find /exp/rmanbackup -mtime +2 -exec rm {} ;
rm /exp/rmanbackup/higfmis_20*
rman log=/exp/script/higfmis_disk.log append  <connect target /;
allocate channel for maintenance type disk;
CONFIGURE RETENTION POLICY TO REDUNDANCY 1;
CROSSCHECK BACKUP;
DELETE NOPROMPT EXPIRED BACKUP;
DELETE NOPROMPT OBSOLETE;
run {
allocate channel ch1 type disk;
allocate channel ch2 type disk;
allocate channel ch3 type disk;
allocate channel ch4 type disk;
# sql 'alter system archive log current ';
backup
    incremental level=0
    database include current controlfile
    format '/exp/rmanbackup/higfmis_%T_%s'
    tag = 'LEVEL0' ;
  sql 'alter system archive log current' ;
#        crosscheck archivelog all;
       backup archivelog all format '/exp/rmanbackup/arc_%t_%s_%p.arc' filesperset = 10;
        delete noprompt archivelog all completed before 'SYSDATE-1';
release channel ch1;
release channel ch2;
release channel ch3;
release channel ch4;

allocate channel ch1 type disk;
backup
   FORMAT '/exp/rmanbackup/cntrl_%s_%p_%t'
    CURRENT CONTROLFILE;
release channel ch1;
}

allocate channel for maintenance type disk;
CONFIGURE RETENTION POLICY TO REDUNDANCY 1;
CROSSCHECK BACKUP;
DELETE NOPROMPT EXPIRED BACKUP;
DELETE NOPROMPT OBSOLETE;


EOF

zz="end time":`date +"%Y%m%d%H%M" `
echo $zz>>/exp/script/higfmis_disk.log