[Info-vax] OpenVMS - DCL - Data entry filtering

[JF Mezei]

On 15-03-29 18:03, Stephen Hoffman wrote:

> MAIL is a (good?) (bad?) example of what happens when you don't have a 
> modern database, when you do have to work within the limitations on how 
> fast you can scan directories (and this also from within a 


But MAIL was originally designed like NOTES, with the expectation that
most messages would be stored in the main indexed MAIL.MAI file.

The size limitations that triggered external storage were fine
originally, but once just about every internet email exceeded that size
limit, the mail store morphed into something it had not been designed
for with every email stored externally.


ALL-IN-1 had an interesting design. Created a database of email documeht
attributes with pointer to random filename stored in a "random"
directory. It was designed that way to distribute the tousands of files
amongst a number of directories to avoid the performance problems of
large directories.

It also had the advantage of having 1 copy of an email sent to multiple
recipients. Each had a pointed to the shared copy. It only got deleted
when the shared count dropped to 0.

Note that Unix mail stores are not exactly very efficient either. But
they seem to work and scale.

dovecit for instalce uses strange file names on OS-X for each message:
"1404580067.M555292P14187.velo.vaxination.ca,W=2670,S=2621:2,RSa"

But it files message files in folders that correspond to IMAP folder
names. and there is some binary index to each file.


VMS designers have to decide whether to go with the flow and just make a
file system very efficient for large number of files (turning the file
system into a database) or  provide database tools that allow apps to
store large number of "things" in a single file instead of one file per
"thing".