Hi Janet,
To answer your question,
With any database or any EJB server, writes queue and happen one at a time.
To go further,
Writes happen one at a time with all databases.
Writes happen one at a time with EJB.
Any number of reads can happen simultaneously with all databases.
One read happens at a time with EJB.
With some databases reads can happen simultaneously with uncommitted writes
and the older committed version of data is returned.
With EJB reads do not happen simultaneously with writes.
>From the point of view of concurrency, some databases are better than
others, all EJB servers are worse than any major database.
>From other points of view EJB servers have advantages.
Brendan
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]
Sent: Thursday, November 18, 1999 10:10 AM
To:
[EMAIL PROTECTED]
Subject: Re: [ND] TP's and NetD
<< File: pic06777.pcx >>
Thanks Brendan. So is this statement:
> Oracle will serialize 200 requests to update one row.
explained by this passage:
" This enables read only users of the database to view the
old
committed changes to the database while other uncommitted
changes are made. This makes it possible for reads of a
database to never block."
or did you just mean it "queues" up the 200 requests to
update the same row and
processes them one by one?
Thanks,
Janet
(Embedded
image moved Brendan Johnston
to file: <[EMAIL PROTECTED]>
pic06777.pcx) 11/18/99 12:40 PM
To: 'Aby Mathew' <[EMAIL PROTECTED]>
cc:
[EMAIL PROTECTED] (bcc: Janet
Traub/IS/SSC/THD)
Subject: Re: [ND] TP's and NetD
Relational databases have locking and concurrency built in.
If one user has an uncommitted change to a row, other
attempts to update the
row will block until the first user commits or rolls back.
Unlike EJB servers, databases have separate read and write
locks, deadlock
detection and resolution. There are tools in most
relational databases to
kill particular processes, to determine how many locks a
process holds, how
much IO and CPU a process is using, to automatically kill
processes which
use more than some limit of locks, CPU, IO etc for the user
or session.
Some databases (Yes - Oracle, PostgreSQL, Solid, Interbase.
Not - DB2,
MSSQL, Sybase) have versioning. This enables read only
users of the
database to view the old committed changes to the database
while other
uncommitted changes are made. This makes it possible for
reads of a
database to never block.
EJB's are typically non reentrant. This reduces
concurrency.
Brendan
-----Original Message-----
From: Aby Mathew
[mailto:[EMAIL PROTECTED]]
Sent: Wednesday, November 17, 1999 5:43 PM
To: 'Brendan Johnston'
Cc:
[EMAIL PROTECTED]
Subject: RE: [ND] TP's and NetD
Brendan,
Could you elaborate a little on this:
> Oracle will serialize 200 requests to update one
row.
Thanks,
Aby
> -----Original Message-----
> From: Brendan Johnston
[mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, November 17, 1999 2:44 PM
> To: Gregory Bohmer
> Cc:
[EMAIL PROTECTED]
> Subject: Re: [ND] TP's and NetD
>
>
> Gregory,
>
> Standard WebLogic does not come with Tuxedo.
> Oracle will serialize 200 requests to update one
row.
>
> Brendan
>
>
> -----Original Message-----
> From: Curt Springer
> [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, November 17, 1999
11:56
AM
> To: Gregory Bohmer
> Cc:
>
[EMAIL PROTECTED]
> Subject: Re: [ND] TP's and NetD
>
> Standard ND (not using PACs, EJBs, just
using RDBMS/JDBC
> service) has no
> concept of data integrity, AFAIK. It
only
manages
> resources, i.e., how
> many requests are outstanding, and how
many
db
> connections
> are available at
> the moment. What those requests are
doing
is somebody
> else's department.
>
> - Curt Springer, Team ND
>
>
> At 02:39 PM 11/17/99 -0500, Gregory
Bohmer
wrote:
> >Here's a general question for
everybody. I
recognize
> >that BEA WebLogic uses their own TP
Monitor
called
> >Tuxedo to help queue update/delete
requests, and ensure
> >data integrity. What does NetD use?
For
instance,
> >if 200 threads on the server (from
client
> calls) are all
> trying
> >to simulataneously update the same row
in
the
> underlying
> >Oracle database, what kind of queuing
and
the like are
> >occuring in the NetD app server?
> >
> >How does this translate to the
PeopleSoft
PAC?
> >
> >Thanks as always.
> >
> >Regards,
> >Gregory, HHMI
> >
>
>
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