@Maryam wrote:
I'm developing an application with LV & DSC 8.0. I'm logging data, A&E in a citadel database.
As REM1 mentioned in message http://forums.ni.com/ni/board/message?board.id=170&message.id=161528&query.id=15913#M161528 , "DSC 7.x and higher make use of Microsoft's free version of SQL Server in conjunction with Citadel for logging alarm/event data. All other data is stored in Citadel itself and never interacts with SQL Server."
I want to know:
If this version of DSC logs Alarm and events to a MSDE database or citadel?
What are the limits of each data storage source?
If A&E is logged into MSDE, is there any lifespan for it?
When we configure a Project library to log data, alarm and event into a database, automatically data is logged to citadel and A&Es are logged into MSDE?
DSC 8.x logs alarms/events to CItadel. MSDE is the storage mechanism used by CItadel for the alarm/event data. The reason for doing this is the types of data involved. Single-point (non AE) data is stored in Citadel's compressed data files. Alarm/event data, which is a collection of several different data types all bound together, is stored in MSDE to enable faster, more detailed queries of this more complex data. You can access MSDE directly to view your alarm/event data but there is no need to do so. You can access the alarm/event data using the same methods you would access the single-point data. I mentioned MSDE in the referenced post only to explain, partially, why it was chosen.
Limits of each data storage source -
- single-point data - effectively none. Citadel will continue logging this data until it runs out of free hard drive space. The compression of the data, however, makes this fairly difficult.
- alarm/event data -
- using MSDE - there are 2 limits associated with MSDE.
- Your MSDE data cannot be more than 2 Gb per database. This is only the AE data. Your single-point data does not factor into this limit.
- You cannot have more than x MSDE databases per computer. I think x is 12, but I'm not positive.
- upgrading to SQL Server 2005 Express - information can be found at microsoft here. It appears as though this is a free upgrade for MSDE which would, at least, increase the maximum database size if not the database number limit.
- upgrading to SQL Server - to the best of my knowledge there are no limits using SQL Server but it is not free.
There is no MSDE imposed lifespan for your AE data that I am aware of and have found no references to such on the web.
You are functionally correct. When you configure a library to log you choose the Citadel database to use. All data associated with that library is sent to Citadel. Citadel stores the single point data in compressed data files and creates an MSDE database to store the AE data. When you use MAX, or the alarm/event VIs, to retrieve this data all requests go to CItadel which gathers the data from it's respective storage location and returns it to the calling program.
Regards,
Robert
