Changing the lifespan property

[aSquared]

Hi, (I use LV DSC RT 8.2.1)

I have read 'Logging Data with National Instruments Citadel'  (http://zone.ni.com/devzone/cda/tut/p/id/6579)

But I still have 2 questions.

Background - 

I have 14 Libraries that writes data to the Database constantly. ("forever")

I had a database that grown bigger to 130 GB(!), (the rate of storage was 1 GB per day)

I have asked the staff to go through the Variables and adjust to each Variable a logging deadband and resolution,

(I had a lot of Doubles that had a 0 loggin deadband), and succeeded to lower the rate of storage drastically to 0.1 GB per day.

I have created a new Database 10 days ago.

This Database should be also working "forever".

 Question 1 :

This time I want to maintain the Database size small (not bigger than 5 GB).

So, this morning I have changed the Libraries property Lifespan to 31 days (it was set before to 'data always available').

Will the Data that had been stored to the Database in the past 10 days will be overwritten in the future ?

Or that Citadel started a new trace with different properties when I changed the Lifespan property ?

 Question 2 :

I am planning to archive each week separately, so that if one of the staff would want to view data older than 31 days

he will attach the archived Database(s) that corresponds to the period of time that he likes to investigate.

But....

I have noticed that I cannot perform Archive & Destroy because I get the error -

"The operation cannot be completed because the resource is in use by another client".

and I need to remove the process of the Library via 'Variable Manager' in order to perform Archive & Destroy.

So... If someone will attach some old data to the Main Database it will not be possible to delete it without removing the process.

Do you have a better solution ?

Sincerely Yours,

Amitai Abramson

[Hesloppy]

Hi Amitai,

Question 1:

The data should not be written over.  The settings of the database were changed, so it will just start acting according to the new settings.

Question 2:

In order the perform the archive and destroy, you have to not be monitoring the trace in MAX or in the Variable Manager.  You will get the error message you are getting if you have MAX monitoring the trace. 

Does that help?

Best Regards,

[aSquared]

Hi Hesloppy,

Thank you for your reply. 

answer1 : I didn't get from your answer exactly what data should not be written over.

                There is the Old data that was stored while the Lifespan was set to 'always available'.

                and there is the New data that is now stored while the Lifespan is set to 31 days.

                (The change of this Lifespan settings was performed while the database is collecting data continuously)

                will the old data be written over?

answer2 : That is interesting, I will examine it.

                Do I have the ability to stop the process of Clients monitoring the traces (at the server, where the 

                Database is located) through the Network ?

                I will like to make the archive & destroy process of each week programmatically-timed at the Server.

                and it will be difficult to insure that no Client is monitoring traces through the Network.

Sincerely Yours,

Amitai Abramson.

[Hesloppy]

Hi Amitai,

Sorry I was not completely clear.  As shown in the Datalogging:LifeSpan Properties help:

"The database only discards data if new data is logged. This property affects all data from the library stored in the database, not just the most recent data. For example, if you set this property to four days and you have three days of data, the database does not destroy any data. However, if you set this same property to two days from four days and you have three days of data, the database can destroy any data collected more than two days ago."

The old data will be removed if there as the data you collect fills it in.  In your example the 10 days you collected will not be destroyed until you have collected more than 31 days of data.  After that it will be destroyed in the normal cycle. 

I don't know of any way to disconnet other people from the traces.  

Best Regards,