Re: pack fails: Bad magic number in transaction id

On Monday 16 October 2006 15:27, Poor Yorick wrote:
> Hi,
> 
> When I try to pack my directoryStorage, I get the error "Bad magic number 
> in transaction id".  Apparently, all the files in my t0 directory
> should begin with 'G@\x07v',   

Yes.

> yet mine begin with various things, as listed below (hex output from xxd).

Interesting. I wonder how this happened? First, I should mention that you are 
the first to report this problem.... Is it likely or possible that this could 
be caused by hardware or user error?

Can you post a selection of those files, and their original file/directory 
names?

> Can anyone offer any suggestions on how to successfully pack the database?  

Step one: make a backup.

If this corruption only affects the t* directories then you should be able to 
recover. Undo information may be lost, however the current state of your 
objects should be intact. If the o* directories are corrupt too then there is 
a more serious problem.

The key to the recovery is the file x/packed, which contains a transaction id. 
DirectoryStorage assumes that the t* files of earlier transactions may not 
exist, and will therefore not raise an exception if the t* files are missing.
(the content of this file is held in self._last_pack. You may find it 
interesting to check out how this gets used in Full.py)

The recovery process would therefore involve:

a. Finding all the corrupt files and deleting them.

b. Replace x/packed with the id of a transaction later than those of the files 
you deleted. I guess copying the file x/serial into x/packed should be OK.

Good luck,




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