HP OpenVMS Systems

Longest RMS indexed file key string?

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The Question is:

 
What is the maximum permissable length for the key value when writing to and
 reading from a indexed RMS file?

The Answer is :

 
  The strict answer to the question is 255 byte.
 
  That written, a key that long is likely to have serious performance
  implications.   Accordingly, the OpenVMS Wizard urges you to review
  RMS concepts in the Guide to OpenVMS File Applications manual.
 
  If, after reading that material, you are still convinced you need a
  key as large as possible, then be sure to consider Key Compression
  and Index Compression, as well as relatively large bucket sizes.
 
 
  References:
 
    HELP/MESSAGE/FACILITY=RMS "key size"
 
    The RMS Reference Manual, under the discussion of XABKEY.
 
      When the data type of the key is string, the total size (sum of
      all sizes) of the key must be less than 256 bytes.
 
    Guide to OpenVMS File applications, and most notably the performance
    considerations and the discussion of idexed files; see chapters two
    and three in the current manual.
 
 

  

     

     
answer written or last revised on ( 10-SEP-2004 )
     
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