[Info-vax] Empty blocks in FILES-11 directory files.

[Mark Daniel]

On 25/9/2022 11:57 pm, Volker Halle wrote:
> Mark,
> 
> if your program reports an error again, you should then carefully examine the directory file in question with
> 
> $ DUMP/DIR/HEADER directory-filename.DIR/OUT=temp_file
> 
>> So I guess to the highest block.
> 
> No, the code reads until XabFhc.xab$l_ebk, which is the EFBLK (end-of-file block). And therefore should not find 'empty blocks'.

As noted in my previous post, yes, indeed.  I missed the end-of-record 
in the end-of-file-block essential element and went on parsing "empty 
records" (I believe) in the zeroed memory.

> Test for yourself: create a directory, populate it with a couple of files until EFBLK becomes > 1, then delete all files in that directory.

I have performed multiple iterations of this scenario and am currently 
using it as a test setup.  Can't explain why initially I felt so 
flummoxed in setting up a test scenario.  Thanks for all the DUMP tools. 
  Don't believe I've used DUMP for file system work in at least 25 years.

> Use DUMP/HEADER to find the start LBN of the directory file and then DUMP/BLOCKS=(START=start_lbn,SIZE=2) disk:
> You'll see, that the blocks beyond VBN 1 of the directory file contain 'old directory data', not zeros and they don't start with DIR$W_SIZE=FFFF

$ DUMP/BLOCKS=(START=n,COUNT=n) DKA100:

confirms your statement.

>>> File characteristics: Contiguous, Directory
>>>
>>> This allows more efficient reads/writes and prevents window turns, when already executing inside the XQP.
>> Still a design consideration then.

I merely meant that directory files (still) must be contiguous.

> Please read the second half of that sentence: I strongly believe you can't do a window turn (which involves the XQP), if you are already in the XQP executing a directory operation. So directory files must be contiguous.
> 
> Once you hit this problem again, feel free to provide some more details.
> 
> Volker.

Thanks to all who contributed to this thread.

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