About data storage

AVEVA Historian uses these structures to store data:

• SQL Server database file (.mdf)
  Configuration information and classic event data is stored in a SQL Server database file (.mdf). When you install the Historian, this database file is created for you and is named Runtime. The Runtime database file is named according to this convention: RuntimeDat_<version_number>_<original_server_name>.Mdf. The transaction log is named: RuntimeLog_<version_number>_<original_server_name>.Ldf. For general information on database files, see your Microsoft SQL Server documentation.

  Note: The Holding database is used internally by the Historian if you import a tag database from an InTouch application. The file names for the Holding database are HoldingDat_<version_number>_<original_server_name>.Mdf and HoldingLog_<version_number>_<original_server_name>.Ldf.

• History blocks
  Processing data (including alarms and events), replication data (if configured), and auto-summary data in history blocks. A history block is a folder containing data files of a proprietary format and, possibly, subfolders. Every history block is bound to a fixed time interval specified at its creation. History block time intervals within the same storage partition do not overlap.

  If no data is acquired, or if a block is deleted, for a certain time period, there may be gaps in the history blocks. These are also known as block gaps.

• Storage Partitions
  A Historian server can be configured to run multiple storage instances at the same time, where each instance is associated with a storage partition (also called a storage shard). A storage partition is a set of folders with history blocks not overlapping in time. Currently two types of storage partition are supported - the Main storage partition for primary data, and Auto Summary storage partition for calculated summaries.

For backward compatibility, AVEVA Historian also supports these data storage structures:

• A2ALMDB database
  Since the release of Historian 2017, alarms and events are stored in Historian data blocks by default. Available since AVEVA Historian 2014 R2 release, you have the option of changing this default (when configuring the Historian) to use the legacy A2ALMDB (SQL) database.