Re: Datafile buffering w/ OSF1

Hi Antti !

Antti Jarvinen wrote:
>
> I'm having a slight swapping problem with digital unix 4.0 and oracle804:
> [ vmstat shows high swapping ]
> ...
> and almost all processes (including ora*) are regularly swapped out and in
> causing pretty ugly slowdown.
>
> I'm thinking this might be a file system buffering problem. Our application
> for most part does things periodically: there are processes that do things,
> then go to sleep() for some time, wake up and begin stressing the DB again.
> Every wakeup seems to cause swapping. Because this application does not use
> files, database is the storage for all necessary stuff then I'm not sure where
> the file access are coming from and therefore:
>
> - does 8.0.4.3.0 on 4.0d open datafiles in such a mode that the filesystem
> does not cache the datafile contents again?
>
> As this uses datafiles in AdvFS-disks, no raw partitions are used.
>
> [...]

I have no special Oracle experience, but I never understood why their preference is to use files for their "tablespaces". IMHO, this will _always_ cause double cacheing (in the Oracle RAM structure plus in the Unix file I/O buffer pool) and so cause problems like you describe.

With our Adabas D, we always recommend using raw partitions (for this and other reasons, one being that file I/O takes more CPU than raw disk I/O in the DBMS case).

Regards, Joerg Bruehe

-- 
Joerg Bruehe, SQL Datenbanksysteme GmbH, Berlin, Germany
     (speaking only for himself)
mailto: joerg_at_sql.de