Re: how to force a log switch

Oracle9i hasn't introduced such a parameter; the best way to achieve what you want below 9i is to resize redo logs to be smaller (which several replies have already mentioned)...

With 9i Data Guard, you have options where you can set LGWR to ship redo log files to the standby, and there is even a mode where redo records (especially COMMIT markers) must be shipped and applied to the standby before LGWR considers a COMMIT on the primary to be complete. In all, there are four basic options with 9i Data Guard:

• LGWR synchronously ships redo records to standby and standby applies redo before transaction considered complete
• LGWR ships redo records to standby before transaction considered complete (standby can apply records at a later time)
• ARCH ships redo log files to standby and standby applies redo immediately
• ARCH ships redo log files to standby and standby applies redo at a later time

The first two options come only with 9i Data Guard in 9i EE; the third option came available with 8i EE (i.e. automated standby management), and the fourth option has been around (unofficially) since Oracle v6 and officially as a supported product since v7.3 (i.e. original standby database option) and is still the only option for 8i/9i SE...

As you can imagine, there are obvious advantages and disadvantages in cost, performance, availability, and complexity to each mode. But one cool thing about the first option is that 9i Data Guard can "switch identities" of the primary and standby (i.e. swap standby into primary role and primary into standby role) almost instantaneously using the ALTER DATABASE SWITCH IDENTITY commands. It's another way of achieving the same high-availability goals as RAC/OPS in an "active/passive" arrangement.

In this sense, the 9i Data Guard product is very much in competition with the 9iRAC product. It will be interesting to see how this competition plays out, both within Oracle as well as amongst customers...

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Sunday, August 18, 2002 9:43 AM

>
> I am not sure if 9i has introduced any such parameter.
> Other than sizing smaller redo log files [but that still doesn't guarantee
> that you get a log-switch every X minutes], you'd have to write
> a DBMS_JOB or a CRON job to do an ALTER SYSTEM SWITCH LOGFILE.
>
> Hemant
> At 06:08 AM 18-08-02 -0800, you wrote:
> >Dear gurus !
> >It's either a Sunday's dead brain or ......
> >Is there an init.ora parameter to force redo logs switch every 3 minutes
or
> >so ?
> >( the reason is that I need frequent log switches in order for the
standby
> >database to pickup changes frequently , i.e. to be "almost" in sync with
the
> >primary DB. And, off course, issuing "alter system switch logfile" in the
> >application is not feasible )
> >Now, i only found parameters related to the frequency of the CHECKPOINTs
and
> >not log switches.
> >Any help , please ...
> >
> >
> >DBAndrey
> >
> >* 03-9254520
> >* 058-548133
> >* mailto:andreyb_at_elrontelesoft.com
> >
> >
> >
> >
> >--
> >Please see the official ORACLE-L FAQ: http://www.orafaq.com
> >--
> >Author: Andrey Bronfin
> > INET: andreyb_at_elrontelesoft.com
> >
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> Hemant K Chitale
> Now using Eudora Email. Try it !
>
> My home page is : http://hkchital.tripod.com
>
>
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> Author: Hemant K Chitale
> INET: hkchital_at_singnet.com.sg
>
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