I have an installation which has two SCADA (Intouch) HMIs and I want to save the data in an SQL Server database which will be in another computer. To be as sure as possible that I have an operating database I'm going to set a SQL Server mirroring. So I will have 2 SQL server databases with a distributor. About this I don't have any doubt. To make it easy to understand I've made an image with the architecture of the system.
Architecture.
My doubt is how do I configure the Alarm DB Logger to make it point, automatically, to the secondary database in case that the principal database is down for any unknown failover.
PS: I don't know if it's even possible.
Configure it the database in Automatic failover. The connection are handled automatically in case of a failover. Read on Mirroring EndPoints
The below Links should have more than enough information.
https://learn.microsoft.com/en-us/sql/database-engine/database-mirroring/role-switching-during-a-database-mirroring-session-sql-server
https://learn.microsoft.com/en-us/sql/database-engine/database-mirroring/the-database-mirroring-endpoint-sql-server
The AlarmDBLogger reads its configuration from the registry, so you could try the following:
Stop AlarmLogger
Change ServerName in registry [HKLM].[Software].[Wonderware].[AlarmLogger].[SQLServer]
Start AlarmLogger
But what about the two InTouch-nodes? What if one of those fails? You would have to make sure one of them logs alarms, and that they don't log duplicates!
The standard controls and activex for alarms use a specific view in the alarm database. You cannot change that behaviour, but you can script a server change in InTouch or System Platform.
Keep in mind that redundancy needs to be tested, and should only be implemented if 100% uptime is necessary. In many cases you will be creating new problems to solve instead of solving an actual problem.
Related
I have a calendar-type WPF program that is used to assign the workload to a team. The events are stored in an Access database and the program is accessed by one person at a time by remotely connection to a computer. The team has grown and multiple people would need to access the program simultaneously. I can install the program on several computers, but where should I move the database? On a software like Dropbox/Onedrive, on a SQL online host? Thanks.
You can use a SQL Server on many Cloud platforms (though I am not sure Dropbox can host SQL Server natively). Azure (Microsoft cloud) is a very mature solution. You still should verify, now that multiple users will be managing data, that the database is backed up a regular basis and that any updates to data should be done within transactions that your code should be aware of. 'Aware of' means that if there is a conflict your code should either resubmit or notify the user that the insert/update/delete failed.
Can one install Microsoft's SQL Server Agent, without a database instance?
(The aim is to reduce traffic to the database. I would like to put the server agent to an other server.)
Thanks for the help.
SQL Server Agent needs to store it's data (jobs etc) in the MSDB database. So you will need one.
If your SQL Agent really is causing such a massive amount of I/O that it's use of MSDB is slowing down overall server performance (which I doubt is the case, but everything is possible if you try hard enough), then you have the option to move the MSDB data files to a separate disk. (Not just a separate logical drive on the same disk, but a separate disk entirely).
I expect there are many other performance improvements possible before you get to that point though. Moving TempDB to another physical disk would be a good start point.
My question is similar. How can I make my "instance" the default instance, so I do not have to qualify my sql server with the instance name. Although, this is not the exact same question, I was brought here looking for an answer and others might be as well. This solution allows you to still have multiple instances, yet define the default instance.
To do this you need to change the TCPIP dynamic port of your instance to the default 1433 port value. Details on this simple procedure using the SQL Server Configuration Manager can be found here:
https://kohera.be/blog/sql-server/make-named-instance-look-like-default-instance/
Service dependency is not enough to guarantee that database clients will find their SQL Server up and running after a system reboot. They may be able to create a connection to the master database, but a specific database may still be in the process of opening (in the recovery mode) and connections to it will be refused for some initial period of time.
The exact duration of the delay is highly variable and depends on factors such as number of databases on the system, recovery mode, LDF file size, or traffic prior to the reboot.
The well known approach to dealing with the dependency on the client is sleeping and retrying. However, this approach does not seem exactly clean or reliable, especially when the clients are diverse in terms of technology and ownership and when this race condition appears only very rarely.
Is there any better way to synchronize the clients with the server start-up, ideally through keeping the SQL Server service in the "Starting" state until all databases have been either opened or marked suspect?
Create a windows service that tries to access the database which does not report itself as having started unless successful in establishing a reliable connection. Basically that service would return an error and the service manager would try to run it according to the service settings.
And now you can depend on that new service in your other services that would guarantee that the database is responsive.
Related questions
In C# what is the best way to determine if a database is up and running?
Update
Also, for a much cleaner way to know if the database is up and running is to check the following value:
SELECT state_desc
FROM sys.databases
WHERE name = 'YourDatabase'
If it says anything but 'ONLINE', then the database is not yet ready. (if it exists at all)
http://msdn.microsoft.com/en-us/library/ms190442.aspx
I am trying to get our DBA's to enable DTC on a cluster of SQL Server 2005. Unfortunately they keep refusing. Their argument that they would need to set up a dedicated host for DTC (Could take months!!) as it is not a matter of ticking a few boxes. Is this true? How intrusive is DTC on a shared environment such as a SQL farm. Do I have an argument against this?
Thanks
Had to tone down the original response your 'DBA' team deserve!
In response to your questions:
Dedicated server - Not at all. Everywhere I've worked with clusters, the DTC service is installed when the cluster is commissioned. Typically it sits in its own resource group or within the cluster group. If in its own group its usually sits on whichever server is hosting the cluster group.
Intrusive? - Absolutely not. It should be installed when the cluster is created, as per MS best practice.
Do you have an argument? - You most certainly do. The links below should cover the why and how for getting it installed:
MSDTC and SQL on a Cluster
Clustered SQL Server do's, dont's and basic warnings
DTC needs to be enabled and running on both sides of the connection. In my organization, it took some research to figure out which four boxes to check and then some hand-holding to get those boxes checked on all db servers, all app servers and most laptops. There's still a couple of hold-out developer laptops... but they're ok as long as they don't write. :)
You should have some driving scenario (such as an atomic multiple database write) to hit the DBA's over the head with. Give them some time to guess at alternatives... then let them know that DTC is the only hammer for this kind of nail.
I'm unsure of the implications of DTC on a SQL farm. I imagine the whole farm could get involved in the transaction if it involves enough data... which can't be a good thing.
I have two database servers running SQL Server 2005 Enterprise that I want to make one of them as mirror database server.
What I need is; to create an exact copy database from primary server on mirror server, so when the primary server was down, we could switch database IP on application to use mirror server.
I have examined "mirror" feature on SQL Server 2005, and based on this article:
http://aspalliance.com/1388_Database_Mirroring_in_Microsoft_SQL_Server_2005.all
The mirror database cannot be accessed directly; however snapshots of the mirror database can be taken for read only purposes. (Prerequisites no. 4)
So how it can be useful when I can't access it when primary server was down?
I've been thinking about creating a regular backup on primary server and restore it on mirror server on hourly basis, but that's quite inefficient (slow) especially if I want an exact copy (since hundreds data's are added once in minute).
Any other suggestion?
EDIT:
Maybe what I mean was a replication thing, not a mirror (thanks JP for commenting)
They are referring to the fact that you can't perform queries on the mirrored copy, but you can get around that limitation by creating a snapshot of the mirrored database. This is often done to create a read-only database copy for reporting uses. You would have full access of the mirror if the primary were to fail, but it will not failover automatically.
Log shipping is another option, which allows you to query (read-only) the standby database without having to create a snapshot.
If I understand your question correctly, you shouldn't have to do that. There are several role switching forms you can use to have your mirror take over as primary. You don't change the IP address at the application level, the cluster itself has a virtual IP address that allows access to the data at any given time (given a reasonable amount of time for the switch over to the mirror from a primary failure). The mirror stays in synch by itself. :) There are good articles here and here on clustering.
Edit: Okay, based on the comments, check out the various options for replication.
Your confusion is common - there's a lot of ways to do disaster recovery planning with SQL Server. I've recorded a 10-minute video tutorial of SQL Server disaster recovery options including log shipping, mirroring, replication and more. If you like that one, we've got a longer one at Quest called Disaster Recovery Techniques but that one requires registration.
Instead of investigating a specific technology here, what you might want to do is tell us what your needs are, and then we can help you find out what option is right for you. The videos will give you an idea of what kinds of information you need to know before selecting a particular solution.
When using only two SQL Servers, you need to do the fail-over manually. The 'backup' database will be usable after you do two things;
Disable mirroring on it
Restore the database with RECOVERY (but without a backup file, this will make the database usable).
Therefore mirroring in this manner does make scense, however it is hard to maintain;
Moving back from the backup database to the primary is a 'pain' as you have to set-up the complete mirroring again using a backup of the redundant server. This is needed to get the primary back up to speed.
My recommendation would be to get a thrid SQL Server into the picture that can act as a witness. The witness will monitor the status of the mirroring databases. Your bonus; you will get automatic failover, and will not have the fail-over (and after fail-over) issues.
If I remeber correct, the witness server can be running SQL Express so no need for the Enterprise version on all three - just the two where the actual mirroring will take place.
Let me know if you need Transact SQL for the commands to fail-over and 'anti-fail-over' in a two server scenario, and I can dig them up.