Why does installing patches take so much space in /var/sadm?

All the files that are replaced by a patch are stored under
/var/sadm/patch/<patch-id>/save so the patch can be safely
backed out. Newer patches will save the old files
under /var/sadm/pkg/<pkg>/save/<patch-id>/undo.Z, for each package
patches.

You can remove the <patchdir>/save directory provided you also
remove the <patchdir>/.oldfilessaved file. Newer patches will not
install a .oldfilessaved file.

Alternatively, you can install a patch w/o saving the old
files by using the "-d" flag to installpatch.

ASGAUR