tdm-write slow down program after some hours

[Gibbi]

hello out there.

i am creating a large project using labview 7.1 / DSC.

i use tdm-files to store data to disk periodically (approximately every 5 minutes).

so, the problem is, that after some hours (5-6)  the writing of the tdm-files seem to stock...the whole process takes longer to execute.

has anybody seen this problem before? is it because of large data amounts?

When the system (Windows XP, 256 MB Ram, Celeron 400) is slow, there is no problem with memory or cpu-usage. both are normal. 

thanks for answers..

gibbi

(btw: upgrading to labview 8 + dsc is not possible, enlarging the system resources is also not possible)

[Jochen]

In fact the system resources are very low and I wouldn't recommend to use this low power computer for a large project at all.

But anyway. Could you please provide some more information about what you are doing?

1. How much data do you write each time?
2. Are you writing always to the same file or do you create multiple files?
3. Do you open and close the file before and after each write operation or are the files kept open?
   
4. Why don't you use the Citadel database for data storage?

Best regards,

Jochen Klier
National Instruments Germany

Message Edited by Jochen on 06-14-2006 11:25 AM

[Gibbi]

hi jochen,

>In fact the system resources are very low and I wouldn't recommend to use this low power computer for a large project at all.

sure, but as mentioned it is not switchable.

>How much data do you write each time?

This varies, but as a minimum it contains up to

- 1 file every 5 minutes

1. Are you writing always to the same file or do you create multiple files?
2. Do you open and close the file before and after each write operation or are the files kept open?
   
3. Why don't you use the Citadel database for data storage?

Best regards,

[Gibbi]

hello jochen,

thanks for fast reply.

>In fact the system resources are very low and I wouldn't recommend to use this low power computer for a large project at all.

sure, but as mentioned it is not possible to change the system.

>How much data do you write each time?

data is flexible but as minimum we write:

1 file every 5 minutes containing 5-40 groups, groups containing approximately  16 channels. Each channel has variable data (dbl-arrays for example) inside. 

>Are you writing always to the same file or do you create multiple files?

no, every write is creating a new file.

>Do you open and close the file before and after each write operation or are the files kept open?

no, it is 1 function-block that gets the data from the main-program and writes it to the tdm-file (open and close at beginning and end)

>Why don't you use the Citadel database for data storage?

citadel is a great tool for logging process-data. but, the project we are realizing need some relational data-stuctures. the labview program provides the manufacturing-information to a database, that is sorting the information into different tabels of the enterprise database. we need dsc in that project to easily connect to different opc servers.

kind regards

gibbi

[Jochen]

Hello Gibbi,

I have searched all of our internal and external support documents but I couldn't find hints for similar behavior. I was thinking of fragmented harddrive space and stuff like that but I don't think that this would have a really strong impact on the write performance (as long as you are not using an extremely slow harddisc).

Could you please create a little test vi that writes dummy data to disc by using exactly the same vis that you are using? Maybe you could increase the write rate to make the issue occurr earlier. If you post this vi here this would be a great help to understand and solve the problem.

Best regards,

Jochen