Datatree MUMPS -- resolve undefined variables to null/empty string?

I'm trying to port some scripts from a modern version of Intersystems Cache back to 1980s Datatree MUMPS. It was written in the context where $ZUTIL(18,2) was set. That is, undefined variables resolve to an empty string, rather than throwing an "undefined variable" error.

Rather than refactor it all to check $DATA, does anyone know whether DTM supports a simi开发者_如何学编程lar feature to automatically resolve undefined variables per process, or globally?

*Update: running "zzswitch +2" did the trick.

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That was tricky one.

Have a look at this document:

ftp://ftp.intersystems.com/pub/cache/DTMtoCache.doc95

It says that equivalent of $ZU(18) in DTM was zzswitch +2 / -2

I obviously can't run DTM now so just try to issue zzswitch +2 and then zzswitch -2 and see how does it affect the way your undefined vars are treated.

PS: I would understand efforts of migrating from DTM to Cache, but going back? Mate it's not even necromancy, it's archeology now.