In addition to David's suggestions, if what you want to do is delete entries in the internal graph catalog so your graph entry numbers don't keep incrementing, you could precede your SAS/Graph code with:
[pre]
proc greplay igout = work.gseg nofs;
delete _all_;
run;
quit;
[/pre]
Which will delete ALL the previous entries. If you do not want to delete ALL the entries, then consult the SAS/Graph documentation for information on how to manage the graph catalog entries.
cynthia