testing for corruption

[Nancy Palmquist]

Jeff,

I have seen corruption that falls into a few categories.

1) a block of records is just bad, usually caused by a bad hard drive sector or 
a FAT table failure that pointed to sector incorrectly.  In this case, the 
records before and after the sector are just fine but the records that did live 
in the sector are ruined.  They all need to be erased and returned to the free list.

2) Corruption during a shuffle - Part of the file is structured be one map and 
part by a second map.  I have seen this in more than one form.  A chunk of 
records in the middle (usually when someone update the data during a shuffle) 
or half right and half wrong.  When the file is increased, the shuffle will make 
the new file in a new place.  When the shuffle is making the file smaller, it 
writes over the existing file, from the beginning.  This crashes part way thru 
and the data file is trashed.

3)  Mismatches between key and data files as to the number of records each counts.

4) this can also apply to the key,  keyx1, keyx2, keyx3 types of file layouts.

I have also seen cases where you can see the data on the screen but the free 
record flag is set to free so the data is not seen by filePro.  That was a 
bugger to fix.  Can not imagine how that happened in the first place, but I saw 
it at least twice.

Sounds like a great tool, but corruption can come in a variety of forms.  Might 
be tricky to figure out what is exactly needed.

Nancy

-- 
Nancy Palmquist 		MOS & filePro Training Available
Virtual Software Systems	Web Based Training and Consulting	
PHONE: (412) 835-9417		   Web site:  http://www.vss3.com