>> it depends how well it caches, actually. does the search speed up
>> after one traversal?

pass.  I've never tested this aspect of directory cacheing.
VMS certainly supports such concepts, but I do know that its
cache is (for example) not as efficient as MS/DOS's which
(if set sufficiently large) can hold an entire file-system
(names, not contents!) in memory.  But this is really an issue
of scaling: an MS/DOS system is sufficiently small that cacheing
all headers is feasible; a VMS system is typically several orders
of magnitude larger, and I think it is unlikely that all headers
would ever be cached simultaneously.  It's too long since I was
a VMS tuner for me to start meaningfully researching this now...

>> um, have you _read_ your copy of the TDS?

No.  Have you read Volumes A, B, C, D, & E from cover to cover?!

>> where there is a problem is if you search
>>   tex/....
>> instead of
>>   tex/<format>/...
>> possibly.

Hmmm; this should be made clear in the instructions for setting
logical names/environment variables...