I have a requirement where the client database changes should be sync with the server (centralized). All clients use only SQL Server Express where as the server is of SQL Server 2008 R2. Do we have any way to do this without Microsoft Sync framework? With sync framework, all data starts from the beginning which is taking longer time.
Without knowing what acceptable latency is, what the network latency/reliability is, whether clients are connected/disconnected, and whether or not changes made at the clients need to be sent back to the server, assuming you want to send incremental changes, you have options database and log backup/restore, transactional replication and merge replication. There may be more, but those are the more common solutions that will synchronize two servers.
If you are looking for bi-directional data flow, then merge replication is the appropriate solution.
Merge replication is typically used in server-to-client environments. Merge replication is appropriate in any of the following situations:
Multiple Subscribers might update the same data at various times and propagate those changes to the Publisher and to other Subscribers.
Subscribers need to receive data, make changes offline, and later synchronize changes with the Publisher and other Subscribers.
Each Subscriber requires a different partition of data.
Conflicts might occur and, when they do, you need the ability to detect and resolve them.
The application requires net data change rather than access to intermediate data states. For example, if a row changes five times at a Subscriber before it synchronizes with a Publisher, the row will change only once at the Publisher to reflect the net data change (that is, the fifth value).
Related
Let's have a classic server-side RDBMS (Oracle/MS SQL/MySQL) and a client side embedded database (e.g. sqlite). We want some tables kept in sync between client and server.
Each server-side table to sync has its counterpart in client-side with the same schema (...or at least similar considering the different data types supported by the database engines). Moreover each table has a timestamp column updated by every update operation.
How can we collect the rows that are updated either server or client side since the last sync efficiently? Efficient meaning
with low bandwith usage, e.g. not sending entire tables back and forth
in a resource friendly way so that the syncing process can be utilized frequently
I have installed SQL server database (mainserver) in one instance and SQL server database for RerportServer in others. what is the best way to replicate data from mainServer to report Server? Data in mainServer changes frequently and actual information in the ReportSever is very important.
And there is many ways to do this:
mirroring
shipping log
transactional replication
merge replication
snapshot replication
are there some best-practices about this?
Thanks
You need Transactional Replication for your case. Here is why you would not need the other 4 cases:
Mirroring
This is generally used to increase the availability of a database server and provides for automatic failover in case of a disaster.
Typically even though you have more than a single copy of the database (recommended to be on different server instances), only one of them is active at a time, called the principle server.
Every operation on this server instance is mirrored on the others continuously (as soon as possible), so this doesn't fit your use case.
Log Shipping
In this case, apart from the production database servers, you have extra failover servers such that the backup of the production server's database, differential & transactional logs are automatically shipped (copied) to the failovers, and restored.
The replication here is relatively scheduled to be at a longer interval of time than the other mechanisms, typically ranging from an hour to a couple of hours.
This also provides for having the failver servers readies manually in case of a disaster at the production sites.
This also doesn't fit your use case.
Merge Replication
The key difference between this and the others is that the replicated database instances can communicate to the different client applications independent of the changes being made to each other.
For example a database server in North America being updated by clients across Americas & Europe and another one in Australia being updated by clients across the Asia-Pacific region, and then the changes being merged to one another.
Again, it doesn't fit your use case.
Snapshot Replication
The whole snapshot of the database is published to be replicated to the secondary database (different from just the log files being shipped for replication.)
Initially however, for each type of replication a snapshot is generated to initialized the subscribing database, i.e only once.
Why you should use Transactional Replication?
You can choose the objects (Tables, Views, etc) to be replicated continuously, so if there are only a subset of the tables which are used to reporting, it would save a lot of bandwidth. This is not possible in Mirroring and Log Shipping.
You can redirect traffic from your application to the reporting server for all the reads and reports (which you can also do in others too, btw).
You can have independent batch jobs generating some of the more used reports running on the reporting server, reducing the load on the main server if it has quite frequent Inserts, Updates or Deletes.
Going through your list from top to bottom.
Mirroring: If you mirror your data from your mainServer to your reportServer you will not be able to access your reportServer. Mirroring puts the mirrored database into a continuous restoring state. Mirroring is a High Availability solution. In your case the reportServer will only be available to query if you do a fail over. The mirrored server is never operational till fail over. This is not what you want as you cannot use the reportServer till it is operational.
Log Shipping: Log shipping will allow you to apply transactional log backups on a scheduled event to the reportServer. If you backup the transaction log every 15 minutes and apply the data to the reportServer you will have a delay of 15+ minutes between your mainServer and Log server. Mirroring is actually real time log shipping. Depending on how you setup log shipping your client will have to disconnect while the database is busy restoring the log files. Thus during a long restore it might be impossible to use reporting. Log Shipping is also a High Availability feature and not really useful for reporting. See this link for a description of trying to access a database while it is trying to restore http://social.msdn.microsoft.com/forums/en-US/sqldisasterrecovery/thread/c6931747-9dcb-41f6-bdf4-ae0f4569fda7
Replication : I am lumping all the replication together here. Replication especially transactional replication can help you scale out your reporting needs. It would generally be mush easier to implement and also you would be able to report on the data all of the time where in mirroring you cant report on the data in transaction log shipping you will have gaps. So in your case replication makes much more sense. Snapshot replication would be useful if your reports could be say a day old. You can make a snapshot every morning of the data you need from mainServer and publish this to the subscribers reportServer. However if the database is extremely large then Snapshot is going to be problematic to deal with on a daily basis. Merge replication is only usefull when you want to update the replicated data. In your case you want to have a read only copy of the data to report on so Merge replication is not going to help. Transactional Replication would allow you to send replications across the wire. In your case where you need frequently updated information in your reportServer this would be extremely useful. I would probably suggest this route for you.
Just remember that by implementing the replication/mirroring/log shipping you are creating more maintenance work. Replication CAN fail. So can mirroring and so can transaction log shipping. You will need to monitor these solutions to make sure they are running smoothly. So the question is do you really need to scale out your reports to another server or maybe spend time identifying why you cant report on the production server?
Hope that helps!
I can't understand the difference between transactional replication and merge replication.
This is my scenario:
In an organization I have a SQL server which need to collect information from different sql servers which are located in different parts of organization or around the city and some report will create according to gathered information.
Data in different SQL servers update every 5 or 6 minutes.
I don't know should I use transactional or merge replication?
Transactional replication delivers incremental changes from a single publisher to one or more subscribers.
Merge replication brings changes from multiple subcribers together into a central publisher.
It sounds like you'll want merge replication in your scenario.
Merge. Each site is a master of it's own data.
Transactional is one way usually.
You need to share information so merge it is...
Edit, after comment
In which case, yes. Your question implies reporting at each location
However, for performance, I'd consider pushing all updates into a queue using a trigger and Service broker. This way, the write to the remote server is decoupled from the local transaction.
I'd like to have some degree of fault tolerance / redundancy with my SQL Server Express database. I know that if I upgrade to a pricier version of SQL Server, I can get "Replication" built in. But I'm wondering if anyone has experience in managing replication on the client side. As in, from my application:
Every time I need to create, update or delete records from the database -- issue the statement to all n servers directly from the client side
Every time I need to read, I can do so from one representative server (other schemes seem possible here, too).
It seems like this logic could potentially be added directly to my Linq-To-SQL Data Context.
Any thoughts?
Every time I need to create, update or
delete records from the database --
issue the statement to all n servers
directly from the client side
Recipe for disaster.
Are you going to have a distributed transaction or just let some of the servers fail? If you have a distributed transaction, what do you do if a server goes offline for a while.
This type of thing can only work if you do it at a server-side data-portal layer where application servers take in your requests and are aware of your database farm. At that point, you're better off just using a higher grade of SQL Server.
I have managed replication from an in-house client. My database model worked on an insert-only mode for all transactions, and insert-update for lookup data. Deletes were not allowed.
I had a central table that everything was related to. I added a field to this table for a date-time stamp which defaulted to NULL. I took data from this table and all related tables into a staging area, did BCP out, cleaned up staging tables on the receiver side, did a BCP IN to staging tables, performed data validation and then inserted the data.
For some basic Fault Tolerance, you can scheduling a regular backup.
Hi can any body tell me what is use of replication in sqlserver2005.
backup and replicaton looks same?what is diference b/w them
Backups are exactly that: backups. They enable you to recover the data if something bad happens.
Replication is another beast entirely. It basically distributes the data across multiple nodes so that each node has a complete, (close to) up-to-date copy of the data.
There are a number of reasons why you would use replication including, but not limited to:
High availability so that, if one node goes down, other nodes can still service requests.
Geographical distribution, meaning your data can be placed close to those that need it. Clients in Belarus don't need to go all the way to Montana to get the data if you maintain a local replica in Belarus (or somewhere close) - this is for performance. You may have 10,000 clients in Belarus - it's quicker to send one copy over than have all 10,000 request data [although this depends on how often they request data].
Prioritization. If your reporting users (bank management) have a lower service level agreement than your customer-facing staff (bank tellers) [and they should], you can put all the management onto a replica so as not to slow down the primary copy.
Replication is used for a different purpose, for example to make reports without putting that load on the 'real' database.
Replication increases system availability. If one set of database is down, you can serve out of replica.
Backup saves you from catastrophic errors such as human error that dropped the production database. Note that in this case, replication won't save you as it will dutifully replicate drop command.
SQL Server replication is the process of distributing data from a source database to one or more destination databases throughout the enterprise.
Replication is a great solution for maintaining a reporting server.
Clients at the site to which the data is replicated experience improved performance because those clients can access data locally rather than connecting to a remote database server over a network.
Clients at all sites experience improved availability of replicated data. If the local copy of the replicated data is unavailable, clients can still access the remote copy of the data.
Replication: Lots of data, fast and most recent.
Backup/Restore: Some data, perhaps a bit slower, and a specific point in time.
Replication can be used to address a number of different scenarios as detailed below.
Just to be clear however, Replication is not the same as Database Backup
Scenarios:
Server to server: Replicating Data in a Server to Server Environment
Improving Scalability and Availability
Data Warehousing and Reporting
Integrating Data from Multiple Sites(Server)
Integrating Heterogeneous
Data Offloading Batch Processing
Server to client: Replicating Data Between a Server and Clients
Exchanging Data with Mobile Users
Consumer Point of Sale (POS)
Applications Integrating Data from
Multiple Sites (Client)
For a full overview of Microsoft SQL Server Replication see the following Microsoft reference.
http://msdn.microsoft.com/en-us/library/ms151198(SQL.90).aspx
Choose the track that is most appropriate to you (i.e. Developer / Architect) and all shall be revealed :-)