Jay Walters wrote:
>
> This might be a little off topic but doesn't sybase the database have some
> built in support for optimistic locking?
Sybase ASE has a timestamp column type (48 bit integer) which is automatically
set on each insert/update. This makes it very convenient when the app. server
wants to do caching while other database users are making direct updates. It is
also monotonically increasing, which is very useful for ensuring correct
synchronization of app. server object caches within a cluster (in the presense
of external updates to the database).
Also, since folks seem to be keen on "my product does this" type of statements:
<vendor>
Sybase EAServer 4.0 will have clustered entity bean (CMP) object caching
that can work in the presense of external updates to the database, together
with app. server controlled OCC to prevent incorrect updates to the data
based on the use of stale cache data.
No proprietary EJB coding (no coding at all in fact) will be required to
use this feature.
</vendor>
Sybase ASE also supports shared (read) locks but it is advisable for maximum
scalability to avoid read locks (as your writers can otherwise be held
back due to livelock if there are many concurrent readers) and use OCC
instead.
> -----Original Message-----
> From: Evan Ireland [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, June 28, 2001 9:40 PM
> To: [EMAIL PROTECTED]
> Subject: Re: To scale or to be correct: that is the question
>
> James Cook wrote:
> >
> > ... I don't think verified updates works in all concurrency situations,
> > but it will handle most of them.
>
> One case where it falls down is where some of the columns don't allow easy
> tests for equality in the WHERE clause (e.g. some BLOB and similar column
> types).
> Timestamps or version numbers are often more useful (and faster).
> ____________________________________________________________________________
> ____
>
> Evan Ireland Sybase EAServer Engineering
> [EMAIL PROTECTED]
> Wellington, New Zealand +64 4
> 934-5856
>
> ===========================================================================
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> of the message "signoff EJB-INTEREST". For general help, send email to
> [EMAIL PROTECTED] and include in the body of the message "help".
>
> ===========================================================================
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> of the message "signoff EJB-INTEREST". For general help, send email to
> [EMAIL PROTECTED] and include in the body of the message "help".
--
________________________________________________________________________________
Evan Ireland Sybase EAServer Engineering [EMAIL PROTECTED]
Wellington, New Zealand +64 4 934-5856
===========================================================================
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff EJB-INTEREST". For general help, send email to
[EMAIL PROTECTED] and include in the body of the message "help".
