oracle - mysql comparison

[Daniel Morgan]

Re: oracle - mysql comparison

> Well, commercial companies are using the tool successfully, making tons[color=blue]
> of money. We can grump whatever we want (I'd be happy to see everybody
> using Oracle), but the tool is a commercial success.[/color]

Based on your definition we should all be impressed by Microsoft
technology too. Commercial success means good sales and marketing
not good technology. Not that the two can't coexist ... but in this
case the success is related to the fact that the tool is free and
little else.

I have yet to see anyone recover from MySQL or PostgreSQL after a
crash without losing transactions: Not once. And if you think you
can ... give me a byte editor and five minutes and I'll be glad to
see if your belief system is valid.

Daniel Morgan

[Alex Filonov]

Re: oracle - mysql comparison

afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407131327.363b 8e5a@posting.go ogle.com>...[color=blue]
> joel-garry@home.com (Joel Garry) wrote in message news:<91884734. 0407121512.779d e651@posting.go ogle.com>...[color=green]
> > afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407120722.70d6 9490@posting.go ogle.com>...[color=darkred]
> > > Daniel Morgan <damorgan@x.was hington.edu> wrote in message news:<108941332 0.371216@yasure >...
> > > > Alex Filonov wrote:
> > > >
> > > > >>
> > > > >>No comparison and you have missed the most important questions you
> > > > >>should be concerned about unless you are running a hotdog stand.
> > > > >>
> > > > >>1. Where to we call for support if there is a problem we can't solve?
> > > > >
> > > > >
> > > > > mysql.com
> > > >
> > > > Not exactly the same thing as opening a Level 1 TAR.
> > > >
> > >
> > > I don't know all details of MySQL support, but I think you can get pretty
> > > good support, including phone hotline, for the price comparable with the
> > > price of Oracle support.
> > >
> > > > > Being open source product doesn't mean "not supported". You can buy
> > > > > support contract.
> > > >
> > > > True. But being available 7x24 and able to support you in the way
> > > > Oracle support does requires paying money: And lots of it.
> > > >
> > >
> > > Sure. Oracle support is not cheap either.
> > >
> > > > >>2. How do we recover transactions that occur between the last backup
> > > > >> and the time when the system fails?
> > > > >
> > > > > There is limited crush recovery.
> > > >
> > > > Compared with Oracle ... very limited. And it is the issues related
> > > > to Murphy's Law that are most important to consider.
> > > >
> > >
> > > Judging by industy experience (Yahoo! and Google are both using MySQL
> > > on a big scale), things aren't that bad...[/color]
> >
> > They are if you care about transactions and consistency. Yahoo and[/color]
>
> This sarcasm is obsolete. MySQL has pretty decent transactional support.
> As for consistency (I suppose you mean read-only), it's implemented in
> ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS[/color]

It's PostgreSQL, sorry.

[color=blue]
> (DB2, MSSQL) don't have read-only consistency and sell pretty well at that.
>[color=green]
> > Google don't have to. <sarcasm> If you miss a web page here or there,
> > so what? Lose a sale in the middle, who cares, the customer will call
> > if he's unhappy, soon enough. Mailing lists? Blame it all on spam
> > filters.</sarcasm>
> >[/color]
>
> Well, commercial companies are using the tool successfully, making tons
> of money. We can grump whatever we want (I'd be happy to see everybody
> using Oracle), but the tool is a commercial success.
>[color=green][color=darkred]
> > >
> > > Myself, I wouldn't recommend MySQL for critical applications as yet.
> > > But things are moving pretty fast in the Open Source world...[/color]
> >
> > Once you build that handbasket, Hell isn't far.
> >
> > jg[/color][/color]

[Alex Filonov]

Re: oracle - mysql comparison

"VC" <boston103@hotm ail.com> wrote in message news:<KbZIc.816 43$Oq2.30187@at tbi_s52>...[color=blue]
> Hello,
>
> Please see in-line:
>
> "Alex Filonov" <afilonov@yahoo .com> wrote in message
> news:336da121.0 407131327.363b8 e5a@posting.goo gle.com...[color=green]
> > As for consistency (I suppose you mean read-only), it's implemented in
> > ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
> > (DB2, MSSQL) don't have read-only consistency and sell pretty well at[/color]
> that.
>
> Please define 'read-only consistency' and elaborate a bit on why DB2 and
> MSSQL don't have it.
>[/color]

Read-only consistency is defined well enough in Oracle Concepts document.
In short, it means that result of any query reflects commited data in the
tables as of time when the query was submitted, without locking any objects
in the database (readers don't block writers, writers don't block readers).

DB2 and MSSQL can do either dirty read (including uncommited changes) or
consistent read with lock (read commited). To my knowledge, only PostgreSQL
and Interbase have read-only consistency in Oracle definition.

As for why... I don't work (and never did) for either IBM or M$, so I
don't have an answer to this question.
[color=blue]
> Thanks.
>
> VC[/color]

[Five Cats]

Re: oracle - mysql comparison

In message <336da121.04071 41111.67a9ab79@ posting.google. com>, Alex
Filonov <afilonov@yahoo .com> writes[color=blue]
>"VC" <boston103@hotm ail.com> wrote in message
>news:<KbZIc.81 643$Oq2.30187@a ttbi_s52>...[color=green]
>> Hello,
>>
>> Please see in-line:
>>
>> "Alex Filonov" <afilonov@yahoo .com> wrote in message
>> news:336da121.0 407131327.363b8 e5a@posting.goo gle.com...[color=darkred]
>> > As for consistency (I suppose you mean read-only), it's implemented in
>> > ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
>> > (DB2, MSSQL) don't have read-only consistency and sell pretty well at[/color]
>> that.
>>
>> Please define 'read-only consistency' and elaborate a bit on why DB2 and
>> MSSQL don't have it.
>>[/color]
>
>Read-only consistency is defined well enough in Oracle Concepts document.
>In short, it means that result of any query reflects commited data in the
>tables as of time when the query was submitted, without locking any objects
>in the database (readers don't block writers, writers don't block readers).
>
>DB2 and MSSQL can do either dirty read (including uncommited changes) or
>consistent read with lock (read commited). To my knowledge, only PostgreSQL
>and Interbase have read-only consistency in Oracle definition.[/color]

So does Informix IDS, so long as you specify the correct isolation
level.
[color=blue]
>
>As for why... I don't work (and never did) for either IBM or M$, so I
>don't have an answer to this question.[/color]

--
Five Cats
Email to: cats_spam at uk2 dot net

[Joel Garry]

Re: oracle - mysql comparison

afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407131327.363b 8e5a@posting.go ogle.com>...[color=blue]
> joel-garry@home.com (Joel Garry) wrote in message news:<91884734. 0407121512.779d e651@posting.go ogle.com>...[color=green]
> > afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407120722.70d6 9490@posting.go ogle.com>...[color=darkred]
> > > Daniel Morgan <damorgan@x.was hington.edu> wrote in message news:<108941332 0.371216@yasure >...
> > > > Alex Filonov wrote:
> > > >
> > > > >>
> > > > >>No comparison and you have missed the most important questions you
> > > > >>should be concerned about unless you are running a hotdog stand.
> > > > >>
> > > > >>1. Where to we call for support if there is a problem we can't solve?
> > > > >
> > > > >
> > > > > mysql.com
> > > >
> > > > Not exactly the same thing as opening a Level 1 TAR.
> > > >
> > >
> > > I don't know all details of MySQL support, but I think you can get pretty
> > > good support, including phone hotline, for the price comparable with the
> > > price of Oracle support.
> > >
> > > > > Being open source product doesn't mean "not supported". You can buy
> > > > > support contract.
> > > >
> > > > True. But being available 7x24 and able to support you in the way
> > > > Oracle support does requires paying money: And lots of it.
> > > >
> > >
> > > Sure. Oracle support is not cheap either.
> > >
> > > > >>2. How do we recover transactions that occur between the last backup
> > > > >> and the time when the system fails?
> > > > >
> > > > > There is limited crush recovery.
> > > >
> > > > Compared with Oracle ... very limited. And it is the issues related
> > > > to Murphy's Law that are most important to consider.
> > > >
> > >
> > > Judging by industy experience (Yahoo! and Google are both using MySQL
> > > on a big scale), things aren't that bad...[/color]
> >
> > They are if you care about transactions and consistency. Yahoo and[/color]
>
> This sarcasm is obsolete. MySQL has pretty decent transactional support.
> As for consistency (I suppose you mean read-only), it's implemented in
> ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
> (DB2, MSSQL) don't have read-only consistency and sell pretty well at that.[/color]

Sorry, I was in too bad of a mood to be posting at that particular
moment. It seems that some of my stuff in OAS has performance issues
because of waiting on sqlnet in the middle of transactions, and I was
frustrated at not having figured out what was happening yet. I don't
think anyone would have _tried_ to do such a thing with mysql. I'm
not sure if that is good or bad.
[color=blue]
>[color=green]
> > Google don't have to. <sarcasm> If you miss a web page here or there,
> > so what? Lose a sale in the middle, who cares, the customer will call
> > if he's unhappy, soon enough. Mailing lists? Blame it all on spam
> > filters.</sarcasm>
> >[/color]
>
> Well, commercial companies are using the tool successfully, making tons
> of money. We can grump whatever we want (I'd be happy to see everybody
> using Oracle), but the tool is a commercial success.[/color]

Didn't they, like, sell out to SAP? Is that really commercial
success? And I'm yet to be convinced any of the *gres's commercial
viability. As Daniel pointed out, commercial success is not related
to technical superiority.

jg
--
@home.com is bogus.
I'm so tired. http://slate.msn.com/id/2103823/

[VC]

Re: oracle - mysql comparison

Pls. see below:

"Alex Filonov" <afilonov@yahoo .com> wrote in message
news:336da121.0 407141111.67a9a b79@posting.goo gle.com...[color=blue]
> "VC" <boston103@hotm ail.com> wrote in message[/color]
news:<KbZIc.816 43$Oq2.30187@at tbi_s52>...[color=blue][color=green]
> > Hello,
> >
> > Please see in-line:
> >
> > "Alex Filonov" <afilonov@yahoo .com> wrote in message
> > news:336da121.0 407131327.363b8 e5a@posting.goo gle.com...[color=darkred]
> > > As for consistency (I suppose you mean read-only), it's implemented in
> > > ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
> > > (DB2, MSSQL) don't have read-only consistency and sell pretty well at[/color]
> > that.
> >
> > Please define 'read-only consistency' and elaborate a bit on why DB2[/color][/color]
and[color=blue][color=green]
> > MSSQL don't have it.
> >[/color]
>
> Read-only consistency is defined well enough in Oracle Concepts document.
> In short, it means that result of any query reflects commited data in the
> tables as of time when the query was submitted, without locking any[/color]
objects[color=blue]
> in the database (readers don't block writers, writers don't block[/color]
readers).[color=blue]
>[/color]

Ah, that's what you mean. In this narrow sense, yes, you are right. A
more correct way would be to say that Oracle implements a variety of
multiversion concurrency control with 'read consistency' being just a part
of the mechanism.

DB2 and MSSQL naturally do not have this kind of 'read consistency' (in a
narrow sense) since they implement an entirely different concurrency model
which prevent neither from producing fully consistent results, read or
otherwise, in a proper isolation mode/level.


VC

[Alex Filonov]

Re: oracle - mysql comparison

afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407131327.363b 8e5a@posting.go ogle.com>...[color=blue]
> joel-garry@home.com (Joel Garry) wrote in message news:<91884734. 0407121512.779d e651@posting.go ogle.com>...[color=green]
> > afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407120722.70d6 9490@posting.go ogle.com>...[color=darkred]
> > > Daniel Morgan <damorgan@x.was hington.edu> wrote in message news:<108941332 0.371216@yasure >...
> > > > Alex Filonov wrote:
> > > >
> > > > >>
> > > > >>No comparison and you have missed the most important questions you
> > > > >>should be concerned about unless you are running a hotdog stand.
> > > > >>
> > > > >>1. Where to we call for support if there is a problem we can't solve?
> > > > >
> > > > >
> > > > > mysql.com
> > > >
> > > > Not exactly the same thing as opening a Level 1 TAR.
> > > >
> > >
> > > I don't know all details of MySQL support, but I think you can get pretty
> > > good support, including phone hotline, for the price comparable with the
> > > price of Oracle support.
> > >
> > > > > Being open source product doesn't mean "not supported". You can buy
> > > > > support contract.
> > > >
> > > > True. But being available 7x24 and able to support you in the way
> > > > Oracle support does requires paying money: And lots of it.
> > > >
> > >
> > > Sure. Oracle support is not cheap either.
> > >
> > > > >>2. How do we recover transactions that occur between the last backup
> > > > >> and the time when the system fails?
> > > > >
> > > > > There is limited crush recovery.
> > > >
> > > > Compared with Oracle ... very limited. And it is the issues related
> > > > to Murphy's Law that are most important to consider.
> > > >
> > >
> > > Judging by industy experience (Yahoo! and Google are both using MySQL
> > > on a big scale), things aren't that bad...[/color]
> >
> > They are if you care about transactions and consistency. Yahoo and[/color]
>
> This sarcasm is obsolete. MySQL has pretty decent transactional support.
> As for consistency (I suppose you mean read-only), it's implemented in
> ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS[/color]

It's PostgreSQL, sorry.

[color=blue]
> (DB2, MSSQL) don't have read-only consistency and sell pretty well at that.
>[color=green]
> > Google don't have to. <sarcasm> If you miss a web page here or there,
> > so what? Lose a sale in the middle, who cares, the customer will call
> > if he's unhappy, soon enough. Mailing lists? Blame it all on spam
> > filters.</sarcasm>
> >[/color]
>
> Well, commercial companies are using the tool successfully, making tons
> of money. We can grump whatever we want (I'd be happy to see everybody
> using Oracle), but the tool is a commercial success.
>[color=green][color=darkred]
> > >
> > > Myself, I wouldn't recommend MySQL for critical applications as yet.
> > > But things are moving pretty fast in the Open Source world...[/color]
> >
> > Once you build that handbasket, Hell isn't far.
> >
> > jg[/color][/color]

[Alex Filonov]

Re: oracle - mysql comparison

"VC" <boston103@hotm ail.com> wrote in message news:<KbZIc.816 43$Oq2.30187@at tbi_s52>...[color=blue]
> Hello,
>
> Please see in-line:
>
> "Alex Filonov" <afilonov@yahoo .com> wrote in message
> news:336da121.0 407131327.363b8 e5a@posting.goo gle.com...[color=green]
> > As for consistency (I suppose you mean read-only), it's implemented in
> > ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
> > (DB2, MSSQL) don't have read-only consistency and sell pretty well at[/color]
> that.
>
> Please define 'read-only consistency' and elaborate a bit on why DB2 and
> MSSQL don't have it.
>[/color]

Read-only consistency is defined well enough in Oracle Concepts document.
In short, it means that result of any query reflects commited data in the
tables as of time when the query was submitted, without locking any objects
in the database (readers don't block writers, writers don't block readers).

DB2 and MSSQL can do either dirty read (including uncommited changes) or
consistent read with lock (read commited). To my knowledge, only PostgreSQL
and Interbase have read-only consistency in Oracle definition.

As for why... I don't work (and never did) for either IBM or M$, so I
don't have an answer to this question.
[color=blue]
> Thanks.
>
> VC[/color]

[Five Cats]

Re: oracle - mysql comparison

In message <336da121.04071 41111.67a9ab79@ posting.google. com>, Alex
Filonov <afilonov@yahoo .com> writes[color=blue]
>"VC" <boston103@hotm ail.com> wrote in message
>news:<KbZIc.81 643$Oq2.30187@a ttbi_s52>...[color=green]
>> Hello,
>>
>> Please see in-line:
>>
>> "Alex Filonov" <afilonov@yahoo .com> wrote in message
>> news:336da121.0 407131327.363b8 e5a@posting.goo gle.com...[color=darkred]
>> > As for consistency (I suppose you mean read-only), it's implemented in
>> > ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
>> > (DB2, MSSQL) don't have read-only consistency and sell pretty well at[/color]
>> that.
>>
>> Please define 'read-only consistency' and elaborate a bit on why DB2 and
>> MSSQL don't have it.
>>[/color]
>
>Read-only consistency is defined well enough in Oracle Concepts document.
>In short, it means that result of any query reflects commited data in the
>tables as of time when the query was submitted, without locking any objects
>in the database (readers don't block writers, writers don't block readers).
>
>DB2 and MSSQL can do either dirty read (including uncommited changes) or
>consistent read with lock (read commited). To my knowledge, only PostgreSQL
>and Interbase have read-only consistency in Oracle definition.[/color]

So does Informix IDS, so long as you specify the correct isolation
level.
[color=blue]
>
>As for why... I don't work (and never did) for either IBM or M$, so I
>don't have an answer to this question.[/color]

--
Five Cats
Email to: cats_spam at uk2 dot net

[Joel Garry]

Re: oracle - mysql comparison

afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407131327.363b 8e5a@posting.go ogle.com>...[color=blue]
> joel-garry@home.com (Joel Garry) wrote in message news:<91884734. 0407121512.779d e651@posting.go ogle.com>...[color=green]
> > afilonov@yahoo. com (Alex Filonov) wrote in message news:<336da121. 0407120722.70d6 9490@posting.go ogle.com>...[color=darkred]
> > > Daniel Morgan <damorgan@x.was hington.edu> wrote in message news:<108941332 0.371216@yasure >...
> > > > Alex Filonov wrote:
> > > >
> > > > >>
> > > > >>No comparison and you have missed the most important questions you
> > > > >>should be concerned about unless you are running a hotdog stand.
> > > > >>
> > > > >>1. Where to we call for support if there is a problem we can't solve?
> > > > >
> > > > >
> > > > > mysql.com
> > > >
> > > > Not exactly the same thing as opening a Level 1 TAR.
> > > >
> > >
> > > I don't know all details of MySQL support, but I think you can get pretty
> > > good support, including phone hotline, for the price comparable with the
> > > price of Oracle support.
> > >
> > > > > Being open source product doesn't mean "not supported". You can buy
> > > > > support contract.
> > > >
> > > > True. But being available 7x24 and able to support you in the way
> > > > Oracle support does requires paying money: And lots of it.
> > > >
> > >
> > > Sure. Oracle support is not cheap either.
> > >
> > > > >>2. How do we recover transactions that occur between the last backup
> > > > >> and the time when the system fails?
> > > > >
> > > > > There is limited crush recovery.
> > > >
> > > > Compared with Oracle ... very limited. And it is the issues related
> > > > to Murphy's Law that are most important to consider.
> > > >
> > >
> > > Judging by industy experience (Yahoo! and Google are both using MySQL
> > > on a big scale), things aren't that bad...[/color]
> >
> > They are if you care about transactions and consistency. Yahoo and[/color]
>
> This sarcasm is obsolete. MySQL has pretty decent transactional support.
> As for consistency (I suppose you mean read-only), it's implemented in
> ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
> (DB2, MSSQL) don't have read-only consistency and sell pretty well at that.[/color]

Sorry, I was in too bad of a mood to be posting at that particular
moment. It seems that some of my stuff in OAS has performance issues
because of waiting on sqlnet in the middle of transactions, and I was
frustrated at not having figured out what was happening yet. I don't
think anyone would have _tried_ to do such a thing with mysql. I'm
not sure if that is good or bad.
[color=blue]
>[color=green]
> > Google don't have to. <sarcasm> If you miss a web page here or there,
> > so what? Lose a sale in the middle, who cares, the customer will call
> > if he's unhappy, soon enough. Mailing lists? Blame it all on spam
> > filters.</sarcasm>
> >[/color]
>
> Well, commercial companies are using the tool successfully, making tons
> of money. We can grump whatever we want (I'd be happy to see everybody
> using Oracle), but the tool is a commercial success.[/color]

Didn't they, like, sell out to SAP? Is that really commercial
success? And I'm yet to be convinced any of the *gres's commercial
viability. As Daniel pointed out, commercial success is not related
to technical superiority.

jg
--
@home.com is bogus.
I'm so tired. http://slate.msn.com/id/2103823/

[Alex Filonov]

Re: oracle - mysql comparison

"VC" <boston103@hotm ail.com> wrote in message news:<%ViJc.917 42$XM6.50454@at tbi_s53>...[color=blue]
> Pls. see below:
>
> "Alex Filonov" <afilonov@yahoo .com> wrote in message
> news:336da121.0 407141111.67a9a b79@posting.goo gle.com...[color=green]
> > "VC" <boston103@hotm ail.com> wrote in message[/color]
> news:<KbZIc.816 43$Oq2.30187@at tbi_s52>...[color=green][color=darkred]
> > > Hello,
> > >
> > > Please see in-line:
> > >
> > > "Alex Filonov" <afilonov@yahoo .com> wrote in message
> > > news:336da121.0 407131327.363b8 e5a@posting.goo gle.com...
> > > > As for consistency (I suppose you mean read-only), it's implemented in
> > > > ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
> > > > (DB2, MSSQL) don't have read-only consistency and sell pretty well at
> > > that.
> > >
> > > Please define 'read-only consistency' and elaborate a bit on why DB2[/color][/color]
> and[color=green][color=darkred]
> > > MSSQL don't have it.
> > >[/color]
> >
> > Read-only consistency is defined well enough in Oracle Concepts document.
> > In short, it means that result of any query reflects commited data in the
> > tables as of time when the query was submitted, without locking any[/color]
> objects[color=green]
> > in the database (readers don't block writers, writers don't block[/color]
> readers).[color=green]
> >[/color]
>
> Ah, that's what you mean. In this narrow sense, yes, you are right. A
> more correct way would be to say that Oracle implements a variety of
> multiversion concurrency control with 'read consistency' being just a part
> of the mechanism.
>
> DB2 and MSSQL naturally do not have this kind of 'read consistency' (in a
> narrow sense) since they implement an entirely different concurrency model
> which prevent neither from producing fully consistent results, read or
> otherwise, in a proper isolation mode/level.
>[/color]

According to some information M$ is going to implement read-only
consistency (Oracle style) in the next version. As for correct concurrency
model, I remember one project, when data warehouse was build using MSSQL,
everything was almost OK, management was pleased immensely. Until they
started running reports. When management found out that reports practically
stopped online work, mood changed.
[color=blue]
>
> VC[/color]

[VC]

Re: oracle - mysql comparison

Pls. see below:

"Alex Filonov" <afilonov@yahoo .com> wrote in message
news:336da121.0 407141111.67a9a b79@posting.goo gle.com...[color=blue]
> "VC" <boston103@hotm ail.com> wrote in message[/color]
news:<KbZIc.816 43$Oq2.30187@at tbi_s52>...[color=blue][color=green]
> > Hello,
> >
> > Please see in-line:
> >
> > "Alex Filonov" <afilonov@yahoo .com> wrote in message
> > news:336da121.0 407131327.363b8 e5a@posting.goo gle.com...[color=darkred]
> > > As for consistency (I suppose you mean read-only), it's implemented in
> > > ProgreSQL, another Open Source DB engine. BTW, other commercial RMBDS
> > > (DB2, MSSQL) don't have read-only consistency and sell pretty well at[/color]
> > that.
> >
> > Please define 'read-only consistency' and elaborate a bit on why DB2[/color][/color]
and[color=blue][color=green]
> > MSSQL don't have it.
> >[/color]
>
> Read-only consistency is defined well enough in Oracle Concepts document.
> In short, it means that result of any query reflects commited data in the
> tables as of time when the query was submitted, without locking any[/color]
objects[color=blue]
> in the database (readers don't block writers, writers don't block[/color]
readers).[color=blue]
>[/color]

Ah, that's what you mean. In this narrow sense, yes, you are right. A
more correct way would be to say that Oracle implements a variety of
multiversion concurrency control with 'read consistency' being just a part
of the mechanism.

DB2 and MSSQL naturally do not have this kind of 'read consistency' (in a
narrow sense) since they implement an entirely different concurrency model
which prevent neither from producing fully consistent results, read or
otherwise, in a proper isolation mode/level.


VC

[VC]

Re: oracle - mysql comparison


"Alex Filonov" <afilonov@yahoo .com> wrote in message
news:336da121.0 407150733.5db6d e1@posting.goog le.com...
[color=blue]
> According to some information M$ is going to implement read-only
> consistency (Oracle style) in the next version.[/color]

Yes, MS SQL Server is going to have multiversion concurrency control (the
latest Yukon beta actually already has it). It'll be exposed to the user as
SNAPSHOT isolation level.
[color=blue]
>As for correct concurrency
> model,[/color]

A correct concurrency control/model ensures that all the permitted
transactions are serializable. In this sense, databases like DB2 or MSSQL
implement a correct concurrency model albeit at the expense of lower
concurrency in some circumstances. Funnily enough, none of the Oracle
isolation levels can make the same promise, i.e. ensure serializable
transaction histories, in any of its isolation levels. Usually, it's quite
easy to obtain correct results by augmenting an isolation level with
something like 'select for update', though..
[color=blue]
>I remember one project, when data warehouse was build using MSSQL,
> everything was almost OK, management was pleased immensely. Until they
> started running reports. When management found out that reports[/color]
practically[color=blue]
> stopped online work, mood changed.[/color]

Well, there are several possible responses to this anecdote:

1. If the described system was a true data warehouse/DSS, then there
should not have been a problem at all since there should have been no OLTP
activity by definition.

2. On the other hand, if the implementation was a mixed OLTP/DSS project,
then judging by your story, the database architect was not qualified to
design a system like that. His/her being surprised that a locking
scheduler's reads block writes, and vice versa, is akin to a swimmer's being
amazed that water is wet. There are several well-known approaches to the
reporting problem such as replicating the main database to a reporting
database, transaction log shipping, scheduling reports off-hours, etc.

VC

[Daniel Morgan]

Re: oracle - mysql comparison

VC wrote:
[color=blue]
> A correct concurrency control/model ensures that all the permitted
> transactions are serializable. In this sense, databases like DB2 or MSSQL
> implement a correct concurrency model albeit at the expense of lower
> concurrency in some circumstances. Funnily enough, none of the Oracle
> isolation levels can make the same promise, i.e. ensure serializable
> transaction histories, in any of its isolation levels. Usually, it's quite
> easy to obtain correct results by augmenting an isolation level with
> something like 'select for update', though..[/color]

And if this is true why, exactly, would anyone care at the expense of
being able to extract an accurate answer from a database without
performing table locks on all resources?

Daniel Morgan

[VC]

Re: oracle - mysql comparison

Hello Daniel,

"Daniel Morgan" <damorgan@x.was hington.edu> wrote in message
news:1089945278 .134355@yasure. ..[color=blue]
> VC wrote:
>[color=green]
> > A correct concurrency control/model ensures that all the permitted
> > transactions are serializable. In this sense, databases like DB2 or[/color][/color]
MSSQL[color=blue][color=green]
> > implement a correct concurrency model albeit at the expense of lower
> > concurrency in some circumstances. Funnily enough, none of the Oracle
> > isolation levels can make the same promise, i.e. ensure serializable
> > transaction histories, in any of its isolation levels. Usually, it's[/color][/color]
quite[color=blue][color=green]
> > easy to obtain correct results by augmenting an isolation level with
> > something like 'select for update', though..[/color]
>
> And if this is true why, exactly, would anyone care at the expense of
> being able to extract an accurate answer from a database without
> performing table locks on all resources?
>[/color]

I am not sure what specific part of my message the word *this* ('if this is
true') refers to, but assuming it's the last sentence then you surely know
that 'select for update' takes write (TX) lock on all the rows involed A
locking scheduler would take *read* row level locks in similar circumstances
automatically. If my interpretaion is incorrect, please elaborate.

VC
[color=blue]
> Daniel Morgan
>[/color]