Re: Sybase to Oracle

Hi,

  I am not sure how Sybase ensures that data commited make to the database. In Oracle, before you get the "commit complete" message, the Oracle Server ensures that the redo for that transaction from the log buffer is physically written to the redo log files on disk. This is all that is required to roll forward the transaction in case of a database crash.

  In Sybase you can place your data segment and log segment on the same device ( though not recommended ). If it's on a file system, you have two options.

1. If you are opening the file with delayed writes disabled at the OS level for that file, then all the writes ( both data and log ) will be flushed immediately. This could effect performance.
2. If the file is opened with delayed writes, then you could loose comitted data, since the redo may not have been written to disk.

I am not sure whether this is why Sybase recommends you to place the database on raw devices. Just my educated guess :)-

Regards,
Denny

In article <37883FDC.67363FE6_at_bigfoot.com>,   Doug Cowles <dcowles_at_bigfoot.com> wrote:
> One quick question I would like to add to this comparison. Sybase
seems to
> strongly object if you do not put your "devices"/datafiles on raw
devices.
> You don't have to,
> but you get a warning message if you don't. What I've heard is that
this is
> because it guarantees comitted information on the OS level. What is
> Oracle's philosophy on this
> potential problem, since it doesn't seem to care what you put your
datafiles
> on. Why
> doesn't Oracle see the same potential problem Sybase does?
>
> Denny Koovakattu wrote:
>
> > Hi,
> >
> > Look at it this way.
> >
> > 1. Oracle Database/Instance --> Sybase Server
> >
> > Don't consider parallel server because Sybase has no equivalent.
> >
> > 2. Oracle Schema/Users --> Sybase Databases
> >
> > In Sybase the database owns the objects created. You add users to
the
> > database. In Oracle, the objects are owned by the user creating it.
You
> > can grant permissions to other users.
> >
> > 3. Oracle Tablespace --> Sybase Segments
> >
> > In Sybase you can place objects on segments. For instance you can
> > place a table in a particular segment. In Sybase you create devices
and
> > create segments on that. So you could have multiple segments on a
single
> > device. I am not sure whether you need to create devices if you are
not
> > using raw devices. Got to check that out with our Sybase
Administrator.
> >
> > Regards,
> > Denny
> >
> > In article <7m11fi$uev$1_at_nnrp1.deja.com>,
> > lanceg_at_my-deja.com wrote:
> > > Simple, yet I'm puzzled. After hours of research
> > > I'm stumped.
> > >
> > > What is the deal with Oracle and its definition
> > > of a database? Is it an instance, the server
> > > itself, a datasource? Can you have more than one
> > > db on a single Oracle server?
> > >
> > > Below is how sybase has its architecture, can
> > > some one tranlate it to Oracle? Or point me to
> > > the right direction.
> > >
> > > Basic SYBASE ARCHITECTURE
> > >
> > > 1. A single Sybase Server (11.5)
> > > --- a. first db (ACC_DB)
> > > --- b. second db (Survey_DB)
> > > --- c. third db (Symposium_DB)
> > > --------- c.1 Tables belonging to third db
> > > --------- c.2 Storred Procs belonging to third db
> > > --------- c.3 Rest of the objects......to third db
> > > --- d. forth db (Inventory_DB)
> > >
> > > --------- c.3 other objetcs
> > >
> > > All the dbs are up and running concurrently.
> > >
> > > Thanks in advance.

--
Denny Koovakattu
denny_at_vitalsol.com
http://vitalsol.com/

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Share what you know. Learn what you don't. Received on Mon Jul 12 1999 - 13:06:12 CDT