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Dfu error message - what is it really saying

 
Mike R Smith
Frequent Advisor

Dfu error message - what is it really saying

Running dfu 2.7-A on OpenVMS 8.3 and we got the following message during a defrag:

SYSTEM-W-DEVICEFULL, device full; allocation failure
DFU-E-NOTMOVED, Error moving disk:[dir]file.ext

Does this mean that dfu in working on this file actually caused the disk to fill up or does it mean that dfu in attempting to defrag the file, found that there was not a large enough contiguous file space? Or does it mean something else?

The main thing I am trying to determine is, will dfu actually fill the disk and possibly cause impact to other processes writing to the disk. By the way, yes I know there is a newer version. I am asking this question because I am researching something that happened with the specifications above.

Thanks for any help in advance.
2 REPLIES
Mike R Smith
Frequent Advisor

Re: Dfu error message - what is it really saying

I found the error in the manual. I missed it the first time through.

DEVICEFULL: Device has not enough contiguous free space to move the entire file
John Gillings
Honored Contributor

Re: Dfu error message - what is it really saying

Mike,

For future reference... use HELP/MESSAGE and you won't need to dig out the manual. See

$ HELP/MESSAGE DEVICEFULL

>will dfu actually fill the disk and
>possibly cause impact to other processes
>writing to the disk

In theory, no. DFU does its best to stay out of the way, and back when there are potential conflicts. I suppose there are some very unlikely race conditions, for example, imagine there is a single free contiguous block exactly the right size for a DFU consolidation. DFU grabs it just before some other application attempts to allocate space. DFU does it's consolidation, then releases the old fragmented blocks. In the mean time the victim application has failed with DEVICEFULL.

I'm not sure if DFU sets an allocaion threshold slightly below 100% of the disk space to prevent this type of scenario (I know there are definitely some limits on how much free space must be present for DFU to proceed). It could also be argued that if the above situation did occur, the application and storage were so close to the edge that the failure would possibly have occurred even without DFU.

Bottom line. Storage is cheap. It's a false economy to operate with inadequate headroom.
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