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Conference vmszoo::rms_openvms

Title:RMS asks, 'R U Journaled?'
Moderator:STAR::TSPEERUVEL
Created:Tue Mar 11 1986
Last Modified:Wed Jun 04 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:3031
Total number of notes:12302

3018.0. "Calculate a record number based on its RFA?" by FRSTSC::TLAUER ("I've been designed multi-asking.") Thu Mar 06 1997 09:41

Hi,


given a seq. file with fixed-length records, can i, based on the RFA of any 
given record, safely calculate the number of this particular record? Of 
course i'd have to take into account if i have even/odd-sized record sizes, 
and take care of the block-span attribute. But if my algorithm does the right 
things, do i have to take care of anything else? Would such an algorithm be 
supported? Of course a deleted (=nulled-out) record would count as a valid 
record, but i'm aware of that fact.

This would depend on the right interpretation of the RFA for a seq. file as 
holding a 4-byte vbn and a 2-byte byte offset. I couldn't find that documented 
anywhere, so is this a supported interpretation of an RFA value?


regards,

-- Thilo
T.RTitleUserPersonal
Name		DateLines
3018.1STAR::EWOODSThu Mar 06 1997 11:1327
<<given a seq. file with fixed-length records, can i, based on the RFA of any 
<<given record, safely calculate the number of this particular record? Of 
<<course i'd have to take into account if i have even/odd-sized record sizes, 
<<and take care of the block-span attribute. But if my algorithm does the right 
<<things, do i have to take care of anything else?  Of course a deleted 
<<(=nulled-out) record would count as a valid record, but i'm aware of that fact.

  If your algorithm does the right thing (and your caveats appear to have
  covered all the bases), of course you should be able to generate the correct 
  record number.
  
<<Would such an algorithm be supported? 

  I presume you are asking that if your algorithm was added as functionality 
  in some user's application,  would OpenVMS engineering support it if it didn't work 
  at some future time.  If that is your question, then the answer is no.

<<This would depend on the right interpretation of the RFA for a seq. file as 
<<holding a 4-byte vbn and a 2-byte byte offset. I couldn't find that documented 
<<anywhere, so is this a supported interpretation of an RFA value?

  Its internal representation is not documented (supported) for the very reason 
  that its internal representation may change at some future time.   Now while 
  that is not likely to happen, there is no 100% guarantee.  
  
  -- Elinor