Re: Is using linked server with MSDE the way to go for this problem?
From: Andrea Montanari (andrea.sqlDMO_at_virgilio.it)
Date: 10/28/04
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Date: Thu, 28 Oct 2004 13:08:06 +0200
hi Rick,
"Rick Pinson" <rickpinson@yahoo.com(donotspam)> ha scritto nel
messaggio news:69A042D0-CEF0-4AC8-A210-7BC29A6CD5E2@microsoft.com
> We have a problem and I'm not sure of the best way to solve it. Our
> situation:
>
> We have an ASP.NET application which uses a full SQL Server database.
>
> We want to add the capability for salespeople to initially install
> (in a separate
> procedure) our app locally on a tablet PC with a blank MSDE
> database. We'll figure this part out.
>
> Then, periodically, when they are able to access our
> 'master' ASP.NET app from the road, we would like for them to be able
> to download selected rows from a number of tables from the
> central SQL db to their local MSDE. They would make changes locally
> (offline),
> then reconnect later on and upload the data back to the central db.
>
> I am thinking that creating a linked server temporarily on the master
> db (via a call to sp_addlinkedserver) to transfer this data back and
> forth
> to the MSDE db may be the way to go, but haven't found any specific
> info/case studies/etc. that supports that.
this seems like you want to perform a push operation, from the "master" to
all "remote" MSDE instances...
I'd go the opposite way... when the remote MSDE instance is able to connect
to the "master", add a linked server from remote to master, perform the
operations you need, drop the the linked server...
>In addition, I created an
> MSDE database on
> a tablet PC which is hooked to our network, but haven't found a way to
> successfully 'broadcast' its presence to the SQL Server db so that I
> can create a linked-server definition via Enterprise Manager.
the broadcasting mechanism to propagate server presence over the lan is not
always granted as lot of stuff is involved...
for instance: have a look at ListAvailableServer exposed by SQL-DMO:
ListAvailableServer uses ODBC function SQLBrowseConnect() provided by ODBC
libraries installed by Mdac;
this is a mechanism working in broadcast calls, which result never are
conclusive and consistent, becouse results are influenced of various
servers's answer states, answer time, etc.
Until Mdac 2.5, SQLBrowseConnect function works based on a NetBIOS
broadcast, on which SQL Servers respond (Default protocol for SQL Server
7.0), while in SQL Server 2000 the rules changed, because the default client
protocol changed to TCP/IP and now a UDP broadcast is used, beside a NetBIOS
broadcast, listening on port 1434:
which is using a UDP broadcast on port 1434, if instance do not listen or
not respond on time they will not be part of the enumeration.
Some basic rules for 7.0 are:
- SQL Servers have to be running on Windows NT or Windows 2000 and have to
listen on Named Pipes, that is why in 7.0 Windows 9x SQL Servers will never
show up, because they do not listen on Named Pipes.
- The SQL Server has to be running in order to respond on the broadcast.
There is a gray window of 15 minutes after shutdown, where a browse master
in the domain may respond on the broadcast and answer.
- If you have routers in your network, that do not pass on NetBIOS
broadcasts, this might limit your scope of the broadcast.
- Only servers within the same NT domain (or trust) will get enumerated.
In SQL Server 2000 using MDAC 2.6 this changes a little, because now the
default protocol has been changed to be TCP/IP sockets and instead of a
NetBIOS broadcast, they use a TCP UDP to detect the servers. The same logic
still applies roughly.
- SQL Server that are running
- SQL Server that listening on TCP/IP
- Running on Windows NT or Windows 2000 or Windows 9x
- If you use routers and these are configured not to pass UDP broadcasts,
only machines within the same subnet show up.
Upgrading to Service Pack 2 of SQL Server 2000 is required in order to have
.ListAvailableServer method to work properly, becouse precding release of
Sql-DMO Components of Sql Server 2000 present a bug in this area.
The Service Pack 3a introduced some new amenity in order to prevent MSDE
2000 to be hit by Internet worms like Slammer and Saphire virus and to
increase security, so that Microsoft decided to default for disabling
SuperSockets Network Protocols on new MSDE 2000 installation.
Instances of SQL Server 2000 SP3a or MSDE 2000 SP3a will stop listening on
UDP port 1434 when they are configured to not listen on any network
protocols. This will stop enlisting these servers.
of course, Id suggest you to test your network protocols settings...
-- Andrea Montanari (Microsoft MVP - SQL Server) http://www.asql.biz/DbaMgr.shtm http://italy.mvps.org DbaMgr2k ver 0.9.1 - DbaMgr ver 0.55.1 (my vb6+sql-dmo little try to provide MS MSDE 1.0 and MSDE 2000 a visual interface) --------- remove DMO to reply
- Next message: Stefan M. Huber: "Re: MSDE 2000: Authentication failed despite BLANKSAPWD"
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