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Date:	Mon, 21 Sep 1998 10:11:17 PDT
From:	MDINET!ELMONTE!TomE@mdipo.attmail.com (Emerson, Tom # GPS-MDI)
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com (internet!scoug.com!scoug-programming)
Subject:	SCOUG-Programming: Need help selec

Content Type: text/plain

On Sunday, September 20, 1998 8:09 AM, Peter Skye
[SMTP:attmail!internet!peterskye.com!pskye] wrote:
> I've finally found a DB2 description page at
> http://www.software.ibm.com/data/db2/udb/about.html (it's linked off
the
> main page with a small "About" button).
>
> The DB2 "Personal" edition isn't network-aware and the "Enterprise"
> editions are far more than I need (they're cross-platform).

What do they mean by "not network aware"? Nowadays, I would think that
would translate to "not multi-process aware" since you should be able to
"export" the directory containing the database for access by other
workstations, the program running on the other workstation should "think"
that the data base is on a local drive. From the point of view of the
workstation containing the database, someone accessing the data "from the
network" should appear as simply another process reading a (shared) file.
Someone accessing a file on your system while you are accessing it
locally should look no different (to your system) than two processes on
your own system running concurrently.

Or, to attack this more directly, the database "files" themselves have no
inate intelligence -- they're just bits on a magnetic platter. In order
to access the data, you need the data access program. In this case, the
data access program is DB2. DB2 simply reads bits off of magnetic
platters and presents them to the user in a humanly-understandable way.
But DB2 doesn't go down to the hardware level -- it asks the operating
system to read the bits off of the platters and THEN it translates this
to something the human-at-the-keyboard will understand. So in reality,
DB2 shouldn't NEED to be "network aware".

However, DB2, "network aware" or not, should honor file locks since it is
feasible that two or more instances of DB2 may be accessing the same
file. [Note that when I refer to an "instance of DB2", I also include a
user-written program making use of library procedures to read the data
file(s) as "an instance".] Again, file locking is the responsibility of
the OS, not the application (but it is the app's responsiblity to CALL
the lock procedure at appropriate times).

When you export/publish/share (or whatever term you want to use) a drive,
you're basically telling the network that your computer has files
available for access. When you use an exported/published/shared drive,
you're telling your local machine to treat that data as if it were on a
local drive. It is possible, through system calls and what not, to
determine if the file(s) you are accessing reside on truly local drives
or on drives that are on "the network". Applications rarely need to know
this much information about the file(s) it is using -- apps generally
need to open, read, write/update, and close files (and occaisionally
detect EOF :) )

So, the question then becomes is "did IBM ADD code to explicitly check to
see if the file(s) being accessed reside on a truly "local" drive?"
(and, obviously, refuse to work if they aren't)

>
> That leaves:
> $999 DB2 UDB Workgroup Edition V5
> 999 DB2 Universal Developer's Edition V5
>
> The descriptions on the IBM site are:
> - DB2 Universal Database Workgroup Edition--a multi-user
> DB2 database for applications and data shared in a
> workgroup or department setting on PC-based LANs.

This one sounds like it knows about AND honors file locking -- implying
the "personal" edition might not!

> - DB2 Universal Developer's Edition--provides all the
> tools required for one software developer to develop
> client/server applications to run on DB2 Universal
> Database and business tools and applications for a
> company's business on any supported platform.

But this version sounds like it has more "tools" for development.

> If I buy these two packages, do I get the functionality that I want?
> - a database, like dBase or dbExpert.
> - works both standalone or on a network.
> - I can write programs for it in both C++ and Java.
> - I'll be "really cool".
>

I think others have answered this last set of questions... :)

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