How to use "Days to keep historical data" & "Maximum time between logs(hh:mm:ss)

[Ravinder Jagdev]

Iam using LabVIEW DSC. Values are being logged continously into citadel.
Is it possible to retain data of just one month and delete the earlier data as fresh data is being logged into citadel?
Is it possible to achieve this feature with "Days to keep historical data" & "Maximum time between logs(hh:mm:ss)" options in the history menu of Tag configuration editor ?

[mrak1]

Sure.. you should be able to specify the "Days to keep historical data". However, the data will only be marked as old and will be overwritten over time. In other words, you will not see the previous month of data disappear immediately until new data overwrites it.

One other thing that you should consider is archiving. A destructive archive allows you to remove data from the database but store it somewhere else. Check out the Overview of Archive Methods and Using Max to Archive and Merge.

Good Luck,

Mike

[Khalid]

Yes, Days to keep historical data does what you are looking for. After the specified number of days, the old data gets overwritten with new data. So, you always have only the specified number of days' of data in Citadel.

Note: You may sometimes see that old data doesn't get overwritten till after a day or so of your setting (depending on how much data is being logged). This is because Citadel logs in "pages" and waits till the current page it's logging to is full before it starts overwriting the old ones.

You do not have to use the 'Max time between logs' option for this. This option forces Citadel to log data every so-many hh:mm:ss regardless of whether or not the data has changed. Note that this is NOT a way to "log data on
demand". Because, this periodic logging of data would change for a particular tag when its data changes. So, even with this setting all data may not get logged at one shot. Anyways, as I said, you do not have to use this setting for what you're trying to do.

Regards,

Khalid