Future archives

Creating future archives

To manage future data that is not continuous or sequential like real-time historical PI point data, Data Archive uses separate archives called "future archives" that are created automatically. Future archives have pre-determined time ranges and are created only when data is received. Every future archive has an initial size of 1 MB, grows dynamically, and has a time range always bound to one calendar month. For example, if a new PI value comes in on January 7th at 08:00 AM and an archive file does not already exist for the month of January, Data Archive creates one automatically. Future archives are optimized for non-sequential data unlike real-time data stored in "historical" archives. Historical and future archives can be managed independently based on your specific needs for data retention, availability, performance, and reliability.

Data in future archives is never mixed or interchanged with data in historical archives. When time passes and forecasted data moves into the past, it is still stored in the same future archives; Data Archive does not discard or move the data.

In rare situations, you may want to manually create and register future archives because either the initial size or the duration are not desirable. The automatic algorithm will fill in any “gaps” before and after all existing future archives, and re-align new archives to calendar-month duration. For example, if you manually create a future archive from 11:00 AM on January 7th to 09:00 AM on January 14th, Data Archive automatically creates an archive file from 12:00 AM on January 1st to 11:00 AM on January 7th and a second archive file from 09:00 AM on January 14th to 12:00 AM on February 1st. Data Archive only creates these adjacent archives if data is actually received for both of those time ranges.

Archive administration

You can manage historical and future archives by using the PI SMT Archives plug-in or command-line utilities.

• PI SMT Archives plug-in

  The PI SMT Archives plug-in organizes archives by server and type of archive: whether historical or future.

  As a PI system administrator, you must choose the location for future archives and ensure that the Data Archive server has enough disk space. This option is also available during the Data Archive installation process. Future archives are created in the default location PI\arc\future and have the default filename "server-name_datetime-stamp". Optionally, you can also customize the archive file names.

  To change the location of your automatically created archives, in PI SMT, go to Operation > Archives, click to expand the Review and update parameters section, and enter the new location in Auto create path. Run the command pidiag- updateFolderSecurity to make sure proper permissions are set on the new path. Changes to archive location take effect the next time an archive is created. Existing archives are not moved.

  Run the command "pidiag -updateFolderSecurity" to make sure proper permissions are set on the new path.

• Command-line utilities

  Most command-line tools take an extra parameter: -hist or -future. This parameter restricts a command to perform its action against the specified PI point or archive. For example, consider the piartool command for listing archives:

  • Use piartool -al to list all archives.

  • Use piartool -al -hist to list only archives relevant to historical tags.

  • Use piartool -al -future to list only archives relevant to future tags.