On Nov 11, 13:04, George/Jorge wrote:
> Subject: ORACLE, MINI-SQL, INGRES Comparison
>
> As a user of ORACLE, I am looking for information about what I consider
> to be the major RDBMS and their usage of STRUCTURES ( ISAM, CISAM, HEAP,
> HASH, ....) foreign concepts to ORACLE. How does the usage of these
structures
> affect the performance of the system ?  I know what theory says, but I am
> look from the users point of view.  I also want information of the
> usage of ORACLE tablespace, to how Ingres and Mini-sql handle tables in
> separate files and their manipulation. What is better, the tablespace
> concept of the 'others'?

If I understand you correctly you are asking two questions:

1. What good is HASH, ISAM, HEAP?

In Ingres the normal vanilla keyed structure is BTREE.  It does the job
most of the time.  The other structures are enormously useful when you
need to do something special:

HEAP is the "no structure" structure and is good for bulk loading.
HASH is probably the fastest for exact-key matching, is good for insert-a-lot/
delete-a-lot situations, and has unusual locking properties which are very
useful in certain cases.
ISAM is a good keyed structure for static data when you need range
searching, partial key matches, etc and aren't doing much insert/delete.

So are these alternate structures useful in real situations?  yes, all of them.


2. Which is better, the tablespace concept or using regular files?

I don't claim to know how Oracle does tablespaces but I can tell you that
80% of the reason that our product (TelesisMFG) uses Ingres instead of
Sybase was that I blew up the Sybase server 50 ways from Sunday trying
to manipulate the *&@#$& database areas when we were doing the DBMS eval.
I wasn't impressed.  (Yes, yes, sybase people, I did something stupid,
but my point was "why am i doing this")

Using files like Ingres does is just a lot easier to administer.  You
can move things around at the filesystem level without bothering to
tell the DBMS.  Yes I know in theory you have the inode-update overhead
but I think most real Unixes today have workarounds that avoid the
inode update.

If I'm a system administrator I want to be able to move my disks around
without having to run to the DBA (DBA?  what DBA?  who does he work for?
how do I get him to pay attention? ...)  so that the DBMS can deign to
notice the disk changes.  Ingres isn't quite filesystem-layout-ignorant
but it's close.

-- 
Karl Schendel            Phone: (412) 963-8844
Telesis Computer Corp      Fax: (412) 963-1373
wiz@telesis.com

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