Alarm and event data are contained in files with the Ale prefix. Files with the *.adx extension can be regenerated if they are lost or damaged. Citadel 5
Each distinct piece of alarm and event data is composed of several fields of data of varying types. Although Citadel can store numeric data efficiently, Citadel is not optimized for storing record-based data. Storing alarm and event data in the primary Citadel format can lower efficiency and provide a less than optimal mechanism for returning alarm data for viewing.National Instruments stores alarm and event data in an attached Microsoft SQL Server 2005 Express Edition (SQL Server Express or SSE) relational database. SSE is freely redistributable and therefore does not impact the pricing of the DSC Module. SSE can be upgraded to Microsoft SQL Server if necessary. National Instruments recommends that you treat the attached SSE database as a part of Citadel and access it via the API provided with the DSC Module.The alarms and events portion of a Citadel database is limited to 4GB. The SQL Server Express database imposes this restriction. If you require more than 4GB alarm and events in a single Citadel database, you can purchase SQL Server 2005 Workgroup Edition from Microsoft, which removes the 4GB restriction. Caution: Do not modify, move, or delete a database file while the database is attached. Doing so results in a database corruption. If you modify or delete a database file while the database is detached, you might not be able to reattach the database, and you might lose some or all of the data in the database. If you move or copy a detached database, move or copy all database files.
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