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[KB36]Proprietary archiving: binary and ASCII index files

Tags: Archives

Historical data
14 years ago
By RM
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Applies to:

PcVue all versions.
While the basic content of this article remains valid, details may have changed since it was written.
Summary:

This article describes the relations between index files and data files according to the archiving format (binary or ASCII) of a proprietary archive unit. It also explains how to determine the optimum archiving unit size and its implications.
Details:

The file sizes in an archive unit result from two constraints

  • The maximum size configured for a data file (a parameter of the archive unit).
  • The maximum size of the index files associated with each data file.

The values of each trend variable are stored in memory in a buffer whose size is parameterised.  
For all trend variables in the archive unit, either when the buffer is full or on exiting from the application, the values are written to the Hxxx.DAT files. The corresponding index file Hxxx.IND is then updated.  
The second limit arises from the index file whose size is limited by the number of buffers specified in the file Hxxx.DAT.  
There are two formats of historical data. They generate index files of types Hxxx.IDX or Hxxx.IND as follows:

Proprietary_archiving_binary_and_ASCII_index_files_tableau1

If the files Hxxx.DAT are limited by these buffer constraints, the available courses of action are:  

Proprietary_archiving_binary_and_ASCII_index_files_tableau2

 

Note

Having files of 1 MB should not be a problem (unless the user experiences reduced performance when reading the historical data).

On the other hand, problems (such as flattened trend curves, PC clock delay etc.) may occur with saving the data if at the time of copying the files are large in relation to the capacities of the media used (local disc, network etc.).

Created on: 04 Oct 2010 Last update: 13 May 2024