Lets say we have postgres and mongodb server and we sharded.
How does the database knows the specific database server to query a certain record.
or do we have to implement the logic in application layer
Does it differs for sql and no sql database
databases are divided into two parts.
server and client.
you can have few installed servers on the same machine and even a few on another machine, but every time you wanna use a client you will have to connect to a specific server.
if you connect your app to some DB - your app will act as a client, so you will have to connect from your app to some specific server by specifying a network address and port number.
Either your client/app server can decide which database server to direct the query to based on application-embedded logic, or you can have a coordinator node which your client connects to and which then routes the query as appropriate, based on look-up tables it keeps, and makes it all transparent to the client.
It is your hypothetical setup, we can't know what you did; you have to tell us. Did you use some commercial or open-source add-on to implement this?
Related
I have an application that cannot be modified that connects to a SQL Server database using a hardcoded connection string with windows authentication.
I need to move the database to another server but as I cannot modify the hardcoded connection string - I am looking for something to act as a local connection that will then relay the query to the remote database and return the result back to the app.
The only other way I can see to do this is to upgrade from SQL Server Express and use database replication but that will be expensive option for what I need.
Can anyone suggest any software to do this or recommend an alternative method?
Thanks
Update:
The connection string also uses Windows authentication which will not work on the remote server.
If your workstations don't need access to the old server, you could perhaps solve this with DNS, using a cname record to point the old server name to the new. If you can't do this organization wide, you might be able to use entries in the hosts file on the impacted workstations.
I just saw this in the comments:
the database server is the same machine where the app runs (ie, 'localhost')
In that case, you want to figure out what the connection string is using, and the hosts entry should be able to accomplish this.
In old server you can define linked server, pointing it to new one and create queries to link to remote tables; you can use different credentials for it. You may get some performance problems (esp update statements may slow down).
We have approx. 8 odd SQL Servers used for different purposes like inserting data in 1 server, update in another etc. (or connecting to only that database based on user’s region).
The problem is sometimes query for data needs to be done from multiple SQL Server databases. So say, I have an Id property, and based on the Id data needs to be retrieved from multiple of these 8 servers (if there is an Id match, so basically querying all database).
So basically the server which the user is logged into, will use “Linked Server” functionality and connect to other SQL Servers (with the server which the user is currently on acts as the source SQL Server), and using “UNION” functionality to club all data.
As a lot of transactions is taking place each day, this approach is not feasible, performance wise.
So any recommendations on a better approach to achieve the same above functionality. I read a concept called “Server Groups” but not sure of it.
The application is made in .Net Web Forms using Jquery/Ajax/HTML/API and ADO.NET.
If you have a .net application which is outside these 8 servers can't you establish individual connections and pass the ID from .net app to these servers ?
As far as I know "Server Group" is a concept in SSMS which helps you to group the servers and can run common scripts at same time.
Hey guys i am learning about MS SQL-Server clustering instances. I am wondering if you could add a cluster on a existing instance of SQL server 2012.
I mean is it the whole point of clustered instances: to create a new instance that supports disaster recovery?
I have no experience in clustering a SQL Server (I'm no DBA) so all I can give is a link (brentozar.com - An Introduction to SQL Server Clusters) with a good read.
The main things to take away from this excellent post, written by Kendra Little, and I quote:
Key Concept: A Windows Failover Cluster uses shared storage– typically, this shared storage is on a SAN. When a SQL Server instance is installed on the cluster, system and user databases are required to be on the shared storage. That allows the cluster to move the SQL instance to any server (or “node”) in the cluster whenever you request, or if one of the nodes is having a problem. There is only one copy of the data, but the network name and SQL Server service for the instance can be made active from any cluster node.
Translation: A failover cluster basically gives you the ability to have all the data for a SQL Server instance installed in something like a share that can be accessed from different servers. It will always have the same instance name, SQL Agent jobs, Linked Servers and Logins wherever you bring it up. You can even make it always use the same IPAddress and port– so no users of the SQL Server have to know where it is at any given time.
The link has a beautiful description of a use-case with 2 simple images but I don't want to incorporate the whole post in here. If the quote doesn't make things clear, surf to the link.
Is it possible to create multiple backplanes within Signal-R?
We're working on an ASP.net WebAPI Sass application and are looking to implement Signal-R for "real-time" web functionality. Since we'll be hosting the application a web farm, client-connection state will be managed through a SQL Server backplane.
The application is multi-tenant - but database is not. The application determines which connection string to use and all client requests talk to their appropriate database. Now the code for configuring the Signal-R SQL Server backplane within Application_Start() is:
GlobalHost.DependencyResolver.UseSqlServer(connectionString);
Does anyone know if it's possible to create multiple backplanes with Signal-R, basically loop through each connection string and call the above code?
Thanks for checking this out!
If you need to eliminate the single point of failure, I suggest setting up a failover server in case the primary SQL Server machine goes down. Reference: http://technet.microsoft.com/en-us/library/hh231721.aspx
If you simply need more performance than a single SQL Server instance can provide, I suggest using Redis as the backplane.
In either case, I doubt attempting to use "multiple backplanes" will be helpful, unless you intend to map certain hubs to certain backplanes for load distribution.
I've got a SQLServer Database and an application (.NET) that configures data on that database. On the other hand, I've got an application (VC++) that reads that data from the database and must be 'informed' a soon as possible of any change in the data saved on the database.
I would like to receive a signal from the database engine when some data had been changed by the first app. Of course, I can code some kind of message that comunicates both apps but my question is if exists that mechanism (some kind of ultra-trigger that warns the other app) in SQLServer or in any API for accessing SQLServer (Native, OLE DB, or even ODBC)
PS: Apologize for my english
If your requirements include guaranteed delivery (e.g. no lost events) - you might want to consider an MSMQ based strategy.
Accessing MSMQ from Microsoft SQL Server
http://www.codeproject.com/KB/database/SqlMSMQ.aspx
Microsoft Support Knowledge Base Article: 555070
Posting Message to MSMQ from SQL Server
http://support.microsoft.com/kb/555070
You can use a SQL Agent Job that will notify the other app starting it with sp_start_job. Check this out.