HP OpenVMS Systems

Using FDL Files?

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The Question is:

 
Hello,
 
Consider following situation:
In a business environment you have 4 separate data environments. The fdl's to
 create/convert files are shared in all four data environments, but are only
 tuned for one environment (the production environment). The other 3
 environments are test environment
s containing a reduced data set of the production environment. When using the
 same FDL's for these test environments, you end up with files that are far too
 big for those environments. You could end up creating four different fdl's for
 the same file layou
t, tuned for each environment, but than you have to maintain four times the
 amount of fdl's you have now. Isn't their an easy way to change the allocation
 and extension values in an fdl depending on the environment in which you are
 using the fdl?
 
Kind regards,
 
Wim
 

The Answer is :

 
  For the purposes of this discussion, the OpenVMS Wizard will
  reference an FDL file that contains the structure definitions,
  and an FDL that contains record counts and file allocation
  and related considerations.  In your case, you want the former
  but you do not necessarily want the latter -- you want the
  structure, but you do not necessarily want the file size or
  the other results of a file analysis.
 
  You could very easily edit the contents of the FDL file to
  create the appropriate file -- pre-processing the same FDL
  file, for instance, to generate the required output.
 
  Alternatively, the EDIT/FDL tool can accept the traditional
  input, but it can also simultaneously accept a second FDL
  file, a file containing analysis data -- the analysis data
  is generally acquired using ANALYZE/RMS command targeting
  the data file.  The traditional FDL input to the command
  would contain the file structure, while the analysis data
  would vary by the target file context.
 
  The following shows how to use EDIT/FDL and two FDL files
  (STRUCTURE.FDL and ANALYSIS.FDL) to generate a third
  (AGGREGATE.FDL) FDL file:
 
      EDIT/FDL/NOINTERACTIVE/OUTPUT=AGGREGATE.FDL -
        /ANALYSIS=ANALYSIS.FDL STRUCTURE.FDL
 
 
  A sample analysis FDL file follows:
 
    IDENT "MYDATA analysis FDL file for BIG enviironments"
    FILE;               CLUSTER_SIZE            12
    ANALYSIS_OF_KEY 0;  MEAN_DATA_LENGTH        123
                        DATA_RECORD_COUNT       1234567
 
 
  Another approach to customizing the behaviour of FDL is
  to use the FDL callable interface, and specifically to use
  a small tool to generate the FDL dynamically.  In place of
  static FDL files, a tool generates the file at run-time,
  using the fdl$create call.  Based on the target context
  or user input or other considerations, the tool simply
  selects the appropriate FDL text string(s) to pass into
  the fdl$create routine.
 

  

     

     
answer written or last revised on ( 7-JUN-2002 )
     
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