Re: Advanced Server: file locking

From: Brad McCusker (brad.mccuskerNosp_at_Mcompaq.com)
Date: 05/14/03 

Date: Tue, 13 May 2003 22:37:48 -0400

"John Brandon" <brandon@dalsemi.com> wrote in message
news:03051311074699@dscis6-0.dalsemi.com...
<snip>
> You say that more than one PC user can open the file. I believe that the
first
> user has exclusive rights to the file, subsequent users have read only.
>

Depends on how they open it (read or write). Also depends on whether they
are using Opportunistic Locking.

> What happens - when you flip the two parameters (as below) - to the PC?
On
> VMS it is no longer locked, correct? What about from another PC, is it
locked
> or unlocked? No effect? Does the parameter only affect VMS? Reading
your
> HELP snip I believe that only VMS is affected. Curious.
>
> [PLM]
> ENABLE_OPLOCKING = 0
>
>
I'm not sure you can do this on the PC. Setting this as above disables the
Advanced Server's support of Opprotunistic Locking (OpLocks). OpLocks are
best thought of as client side caching. When the client asks to open the
file it might also request an Oplock. If it gets the Oplock, then, it knows
that it can cahce data on the client side and not worry about what happens
on ther server becuase it has that exclusive OpLock. If the server doesn't
support OpLocks, it simply responds to the client that it is not supported,
and the client makes other arrangements.

This has nothing to do with the caching that the Advanced Server performs on
the server side.

> This also disables caching.

Not really, see above.

>What kind of impact does this have? Slower
> response time?

Potentially huge, depending on what the client does if the server doesn't
support OpLocks. I've seen some clients that revert to using many, many
very small transfers. In that case, the performance impact is huge. Other
clients aren't impacted as severly.

Regards,

Brad McCusker
Hewlett-Packard Company
OpenVMS Engineering
Nashua NH USA

>
> John Brandon
> VMS Systems Administrator
> Dallas Semiconductor
> first.last@dalsemi.com
> 972.371.4172 wk

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