How to clear some disk space from device. wanted to clear disk space from $1$dga7: but don't what command should i used.The disk almost full and it effect when i'm trying to increase tablespace on oracle. Please advise $1$DGA7:(HSIBD3) Mounted 0 CERT01 2.22MB

There are two commands for removing files.
PURGE & DELETEPurge will remove multiple versions of a file and save the latest version.
PURGE/KEEP=n file ( will save n copies of the requested file )
In your case, a PURGE would be the first command to use.
PURGE $1$DGA7:[000000...]*.*/KEEP=3
If this command doesn't help you, you need to investigate the disk file by file to determin what files to delele......
$ HELP PURGE
$ HELP DELETE
