mmap, more questions .....

[Ben Duncan]

Thanks Roger. To address a few issues:

Windows - No WAY. I guess I'll do a reverse Bill Gates's and declare SLAG
will MOST definitely not be DESIGNED to run on a WINDOWS server (client
program from WIndows to the *NIX server, yes).

On some off-lists suggestions about using MySql/Postgres/SQLite, I am fully
aware of those databases and their capabilities. However, since the initial
thrust here is to "replicate" Appgen in an Open Source Environment, a
"multi value" data file manager is going to be the easiest for migration
purposes. It will also give to the FOSS community a real PICK like database
engine. Hence the effort to create from tdb a MV data engine.
There is also the fact SLAG is just a bunch of UI into S-lang and any number
of databases can be tied to SLAG. I am just wishing to avoid the crap from
the end user of "My stepson's first cousin is a real ACCESS and PlayStation wizard
so I had him tweak our SQL database and now YOUR programs don't work anymore"
syndrome.


Now on to MORE questions about mmap.

According to the docs I am reading, mmap allows files to be shared by a common
mmap allocation to multiple processes, is this true?
How does it handle if program A opens an mmaps file DATA, then program B opens
file DATA, then program A terminates, does mmap of DATA stay active? When does
it get released?

IF I need to have a file HEADER (not A record/row) in memory, so certain
parameters can be kept (exclusive usage lock semaphores,etc) as well as
the "current record" I am working with, how can that be handled?

What happens and how do you handle the case where program A has
record 1 called up and program B needs record 10000?

On a NOTE of good fortune. The Mississippi Department of Wildlife,Fisheries and
parks, of whom have been running Appgen in their Distribution Center for the last
past 10 years, have decided to renew my Support contract for a period
thru next June despite the fact I am no longer an authorized Appgen VAR. This
is with the understanding that SLAG and the necessary conversion / applications
will be completed by that time .....So ... SLAG has it's first customer ...


Roger Oberholtzer wrote:
> On Wed, 2005-08-03 at 08:52 -0500, Ben Duncan wrote:
> 

> 
> So, go the mmap route. It is portable to any Unix/Linux and even
> Windows. Not that the latter is any concern, I guess.
> 
> 
-- 
Ben Duncan   - VersAccounting Software LLC 336 Elton Road  Jackson MS, 39212
"Never attribute to malice, that which can be adequately explained by stupidity"
        - Hanlon's Razor