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RE: Re: Oracle vs Mysql

From: Grant Allen <>
Date: Tue, 20 Jan 2004 14:29:45 -0800
Message-ID: <>

> -----Original Message-----
> From: []On Behalf Of
> Sent: Tuesday, 20 January 2004 23:59
> To: Multiple recipients of list ORACLE-L
> Subject: Re: Re: Oracle vs Mysql
> if Oracle is offshoring its develeoping of its database,
> everyone else will also... so much for job security.
> anyone I heard postgre sql has multi-versioning? Is it
> implemented like Oracle?

No, its implementation is different. For deletes, it doesn't reclaim space immediately. Instead, it marks a flag indicating at what point (analogous to SCN) the row became deleted, and relevant transactions can still see the row, whereas future transactions can't. Works quite well in practice. The obvious question is "what happens to these rows once all transactions have moved on?". Currently, there's a maintenance job (called Vacuum) that needs to be run to reclaim the space ... at the last week there was a presentation that showed a new lazy daemon that would do this automagically. Updates are handled as a delete+insert, with similar control. One big benefit - you'll never have to size a rollback/undo tablespace, or see 1555 errors :-) :-) :-)

> So UDB is the new DB2? Oracle claims that DB2 is not one
> database but a different database for different Operating
> Systems, is this true? Is it true with UDB?

It used to be, but IBM is tidying things up. The Linux/Unix/Windoze stuff is all identical (it's the old "common server" reborn), and they've made a big effort at harmonising the zOS (and to a lesser extent, AS400) forms. The biggest improvement in the last couple of years was ANSI standard stored procedures (ANSI "Stored Persistent Modules"). Very nice - the structured error handling alone is amazingly good. You can still find the occasional "version lag", where one platform won't have a new feature until a minor version later than another.

(my coffee coaster has something written on it ... "IBM DB2 Certified Database ... " ... what the *#&^$!?!?) :-)

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Author: Grant Allen

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Received on Tue Jan 20 2004 - 16:29:45 CST

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