I am new to SQL and to SQL server and I am using the book to build my knowledge. During early parts of the book, the author has below para. I am confused with the sentence in bold and italics below.
What is the purpose behind running multiple instances of SQL server on a given server? It seems that SQL server is a very costly software, in such case isn't installing multiple instances a costly task?
The Database Engine sits at the core of the SQL Server components. The engine operates as a service on a machine, which is often referred to as an instance of SQL Server. You can run multiple instances of SQL Server on a given server. When you connect to SQL Server, the instance is the target of the connection. Once an application is connected, it sends Transact-SQL (T-SQL) statements to the instance. The instance in return sends data back to the client. Within the connection is a security layer that validates access to the data as specified by the database administrators (DBAs). The Database Engine enables you to leverage the full capabilities of all of the other components, such as accessing, storing, and securing the data..
You might want to run various versions of SQL Server, e.g. 2008, 2008 R2 and 2012 simultaneously in parallel on a given machine. If you're e.g. a consultant and your clients use different versions of SQL Server, and you need to be able to get a backup from them, do some work, and send the database back, you have to use the same version as your client does. Backups aren't backwards-compatible, e.g. if your customer uses 2005, you can restore his 2005 backup onto your 2012 server, but you CANNOT return the data back to the client (since the backups are NOT backwards compatible - you cannot restore a 2012 backup on a 2005 server).
Or you might want to run separate instances for e.g. development and testing on the same physical server machine in separate instances (that are quite well isolated from one another). It's a great way to separate two (or more) "worlds" (environments) of SQL Server from one another; you might have all the same databases - but once in the "Development" context (for your dev team, work in progress), and a second time for your Quality Assurance or Testing team. If you have two totally separate instances, it's like having two (or more) servers living on one machine.
Multiple instances of SQL Server on a single physical machine are a great way to have separate environments - both based on the versions (and editions) of SQL Server you might need to support, but also in terms of the use of the instances - development vs. testing vs. demo vs. whatever-else-you-might-have.
Instances are very well protected from one another and don't interfere with each other - each has their own databases, logins, security, etc.
Related
I'm preparing a migration plan to migrate on-premises SQL Server to Azure. On our on-prem there are two sql instance (DevSQL01\Dev and DevSQL01\Demo) running on single VM. Can we create a same scenario on azure, i.e. can we create two SQL instance on a single Auzure SQL VM or is their any other option?
I know i can create a windows VM on Auzre and install SQL Server and create two instance manually, but i like to find out options like managed instance, elastic pool, etc.. has the feature to host named instance by default.
Forgive me if this is noob question, I just started exploring cloud technologies.
On all flavors of Azure SQL PaaS (Managed Instance, DTU-model, vCore, Serverless, Hyperscale) the concept of named instance does not exist. Your best option is a SQL VM where you can run SQL Setup and install multiple instances.
It seems you need it for development purposes, then you may want to install SQL Server Developer Edition to avoid licensing costs as mentioned here. If this will be a Production server, remember to balance memory usage across the two SQL Server instances and leave some memory for the operating system to avoid impact on the server performance.
I'm currently working on a project proposal which would require moving multiple Access databases into a new MS SQL Server database. The idea is to keep the front end program as MS Access so that the users are familiar with the process of inputting data and creating reports.
However, things get complicated in that the internet in the areas where the survey will be collected has poor connectivity and will be out from time to time. I had thought of a few ways of solving this issue but all of them are cumbersome:
1) Having a PC with a router that stores the SQL Server database in offline mode and the data entry PCs connect to the PC with the offline database through the router. The PC with the SQL Server database can then backup the db on the server when it has an internet connection.
2) Adding the data to MS Access databases that can then be merged with the SQL Server at specified increments (this would probably cause some issues).
We've done option 1 before for similar projects but never for connecting to an SQL Server database in offline mode. However, it seems feasible.
My question is: Does anyone know of a way of using Access as a front end application for SQL Server and being able to update data during times without internet connectivity? The SQL Server database would automatically assign primary keys, so, duplicate unique values shouldn't be an issue while syncing the data.
Thanks for your help. I've been having a hard time finding an answer on Google and syncing to databases is complicated at the best of times. I'm really just looking for a starting point to see if there are easier ways of accomplishing this.
I would run a the free editon of SQL express on all laptops. So the Access database would be the front end to the local edition of SQL express. SQL express can be a subscriber to the "main" sql database. You thus use SQL replication to sync those local editions of SQL server to the master server. Of course the main SQL server can't be the free edition of SQL server. So to publish the database for replication, you can't use the free edition, but those free editions can certainly be used as subscribers.
This approach would eliminate the need to build or write special software for the Access application. You thus do a traditional migration of the access back end (data tables) to sql server, and then simply run the Access application local with sql express installed on each laptop. You then fire off a sync to the main edition of sql server when such laptops are back at the office.
The other possible would be to adopt and use the net sync framework. This would also allow sync, and would eliminate the need to run sql expess on each machine. I think the least amount of effort is to sync the local editions of sql express with the main editon of SQL server running at the office (but that office edition of SQL server can't be a free edition).
I have been supporting a product written in VB6 with an Access database for a long time. In many of the installations a mapped drive was used to allow multiple workstations to run simultaneously. Since it seems Microsoft has broken that recently, I need to re-write everything with a new set of tools.
I plan to use VB.net and I would like to use a SQL database this time for the stability. The problem is that the market I sell to cannot / will not support installing full blown SQL Server and all the complexities of managing it.
What I am not able to find any current info about is whether or not SQL Server Compact still exists, whether or not it can be added to a NON web based project and if it will be easy to deploy and be easy to manage like an Access database was.
When I try to follow the directions to add SQL Server Compact to my project, it isn't available in the Data Source drop down list (there are "Simple by ErikEJ" versions listed but they don't seem to work) I have seen SQL Server Compact talked about with regards to web projects but I am building a locally installed .exe. I can't find ANY current info about what flavors of SQL are available right now to add to a local program running over a peer to peer network.
SQL Server Compact is no longer supported and developed by Microsoft, I suggest that you use SQL Server Express, it allows remote connections (if configured to allow it) and has modest resource requirements. Supports a database up to 10 GB of size.
As suggested, SQL Server CE can still be used but is no longer supported. For file-based databases, Microsoft currently recommend SQLite.
For a multi-user system, SQL Server Express is probably your best bet. It's still server-based though, so the server needs to be installed somewhere. For local databases, you can install on the same machine as the application and attach a data file on demand. For multiple clients, you'll need the server installed on a machine accessible to all and a permanently-attached database.
We are working for a client with an asp.net/SQL server application which has been using a SQL Server 2005 system till now. The client has decided to upgrade the database to SQL Server 2008 R2 and has procured a powerful server machine with 16 processors with enough RAM and installed Windows Server 2008 64 bit on the system. Now we are tasked with the installation of SQL Server 2008 on the system followed by migration of the existing DB from the SQL 2005 box. Now I am not a SQL Server DBA nor am I a System Administrator by role. Hence, in spite of reading up a lot of the literature on the net, I am not quite able to make sense of it all or put it in the right order of execution. Can somebody explain me the following items, preferably in terms of bullet lists:
What are the points of consideration during installation of SQL Server 2008, specifically in terms of
Configuring memory usage
Configuring the SQL Server to take advantage of the multiple processors available
Other factors to configure to enable SQL Server 2008 features for performance and scalability
Other points, if any, for configuring the Windows Server 2008 with respect to SQL Server 2008
Note: We will only use the Database Engine services in SQL Server. The applications does not use SSIS, SSRS, etc.
SQL Server will take advantage of whatever processors are available. Processors will be shared between sessions - if all of the work is being done by a single session, then it will all occur on the same processor (to the best of my knowledge - this requires citation).
Memory usage is dynamic by default, meaning that there is no restrication on memory usage. You can limit the memory usage used by the server (right-click on the connection in SSMS and select properties) if needed. This is generally used if the instance is part of a server performing other tasks, such as running other database instances, web service tasks, etc.
SQL server is pretty good it sorting itself out according to its environment. If you are in a position that you need to create a server farm and distribute data and processing between different machines, this is a whole new topic, discussed at length on MSDN and the StackExchange forums.
I have a desktop application (C# .NET 3.5) that uses a SQL server for it's database. I have had a request from the client, however, to make it possible to export the database as it stands, and be able to use it on a laptop without connectivity. They understand that updates to the parent server will not be reflected in these offline clients.
Is there a way I can just save the DataSet's to a binary form and write them to a disk and send those files to the offline clients.
There is an entire line of tools and technologies covering this case, namely the Synch Framework. See Synchronizing Databases. See Getting Started: Client and Server Synchronization for a starting example involving a SQL Server Compact Edition file on the client (.SDF file) that is synchronized with a SQL Server central database. Note that the client won't install anything else other than you application, the SQL Server CE is just a few in-process DLLs that you distribute with your app, nothing nearly as complex as a SQL Express edition on the client.
The good news is that Synch Framework no only allows the client to get their own on-the-go snapshot of the database, it actually allows for changes applied while disconnected to be merged back into the central site.
You could either use Compact Edition (aka. SDF files), or you can save the datasets as XML using the built-in method.
Can't you just take a SQL Server level backup and have them install e.g. SQL Server Express on their laptops and restore the database there?
That way you wouldn't have to do anything special in your app at all - just change the connection string to point to the local SQL Server Express instance, and off you go! No mucking around with serialized data sets and stuff......