Fixed and dynamic archives

Fixed archive files have a fixed size, regardless of how much data they contain. Dynamic archive files grow in size as they get data. By default, PI archives are fixed.

Use fixed archives for all normal operations. The disk space for a fixed archive is allocated at creation time, so an empty archive and a full archive use the same amount of disk space. A fixed archive may or may not participate in archive shifts, depending on its capacity to hold data for all the points in the system. You can add new points to a fixed archive if it is the primary archive.

Fixed archives become dynamic if they are full, if there is sufficient disk space. This process is known as auto-dynamic archive conversion. Auto-dynamic archive conversion is useful, for example, if you need to incorporate backfilled data into a non-primary fixed archive and the archive is full. If a converted archive becomes primary, it converts back to a fixed size. The allocated disk space for archives is not modified.

After a non-primary fixed archive is converted to dynamic and data is backfilled, you can convert the dynamic archive back to fixed using piarchss, the Offline Archive Utility.

The size of a dynamic archive file is flexible, enabling disk space to be allocated only as needed. Dynamic archives cover a specific time range. The archive file grows as overflow records are added, up to a specified maximum size or, at most, 2TB.