I am new to ipad development. I have to develop an app for a client whose employees use ipads.I am to develop this app that would take the data that they have and store it to the main sql server on their server. On researching i came across that people do that once they have their data on ipad and later sync it with their server. I have used sqlite for android before. But that was like a school project. CRUD operations basically. So since i have little knowledge of sqlite i want to pursue this app in this way. My question is can i write an app that will sync temporary sqlite data with server once they sync ? I have more questions..
Thanks.
It is certainly possible to synchronize data between multiple databases.
Generally speaking, you have to record all changes made since the last synchronization (usually done with serial numbers or timestamps), and apply those changes to the other database.
If the same data has been modified by multiple users, you have to resolve this conflict somehow.
If multiple users can add data, you have to prevent duplicates of primary keys.
See these Wikipedia articles for explanations of some related concepts:
Data synchronization
Replication
Change data capture
this Guy may solve the problem, but it only supports Xamarin(iOS or Android).
http://forums.xamarin.com/discussion/5719/sync-sqlite-with-sql-server-merge-replication
Related
I am building a mobile app with the following business requirements:
Db to be stored locally on the device for use when disconnected from
the cloud.
A NoSQL type store is required to provide for future changes without requiring complex db rebuild and data migration.
Utilises a SQL query language for simple programming.
Run on all target platforms - Windows, Android, iOS
No central database server - data to be synchronised by matching two local copies of the db file.
I have examined a lot of dbs for mobile and none provide all these features except Couchbase Lite 2.1 Enterprise Edition. The downside of that is that the EE license might be price prohibitive in my use case.
[EDIT: yes the EE license is USD$35K for <= 1000 devices to that option is out for me sadly.]
Are there any other such products out there that someone could point me to?
The client-side synchronization of local databases done by Couchbase Lite is a way to replicate data from one mobile device to another. Though is a limited feature because it works on P2P. Take as an example BitTorrent, the fastest and most effective P2P protocol. It still has flaws, risk of data corruption and partial data loss. A P2P synchronization would only be safe when running between two distinct applications on the same mobile device.
In case both databases are in the same mobile device and managed by the same application, it would be much simpler. You could do the synchronization yourself by reading data from one and saving in the other, and dealing with conflicts if needed.
I'm curious, why is it a requirement not to have a central database server? You can fine tune what data is shared and between which users is it shared. Here is how it works:
On server-side user registry, each user is assigned a list of channel names. At the same time, each JSON document added or updated is also linked to a list of channel names. For every pair of user x document with at least one channel name in common, the server allows push/pull replications to occur.
Good luck !
Are there any resources available that can guide someone on how to 'think' about the various components of a hosted / cloud solution before going ahead and starting to make a hosted application? If that made no sense, what I mean to ask is are there any guidance books/websites on what things need to be considered when making a cloud application?
I am attempting to make a hosted CRM-style software application that will serve many hundreds of customers. The application is powered by a SQL server database with many tables and a ColdFusion, HTML5, CSS, Javascript front-end. If I was installing this application and its components at each client site, then each installation is unique to that customer. But somehow I have to replicate this uniqueness in the cloud which is baffling me.
Only two things have come to mind so far:
The need for a unique database per customer in SQL server
The need to change DB connection strings per customer in the web application
My thought process has come to a block when I am trying to envisage how to design the application to serve so many different customers. Even though the application that all customers use will is the same (same DB tables, same front-end), the data that they store and retrieve will be specific to them. So I was thinking that surely each customer needs a separate database creating for them? Is it feasible to create a replica database for each customer? If I need to update some tables or add a new table, how would I do this for hundreds of different databases?
From the front-end I guess each unique customer log-in would change DB connection strings so that they can only access their database. Other than this I can't think of anything else that needs to change per customer basis.
When a new customer wants to sign up, it needs to be clear to me what I need to create for them to have access to the application. I guess this is ultimately what I need to think of but I'm stuck.
If anyone can suggest some things to think of or if there is a book or website on this kind of thing that someone could point me to I'd really be very thankful.
EDIT:
I was looking at an article about Salesforce.com and it says
"In order to ensure privacy of data for each user and give an effect of each having their own database, the data from different users are securely isolated from one another."
Anyone know how this is achieved or how it may be done?
Found some great information here. It is called multi-tenant database design and seems to be a common topic. Once I get the database designed then the application can sit nicely on top.
https://dba.stackexchange.com/questions/1043/what-problems-will-i-get-creating-a-database-per-customer
I have a database-driven site developed with MVC and Entity Framework code first. The database is rather large and contains all the data that I would need for an additional web application. What are the implications of setting up a new website with database first using the same existing database? What I am really trying to ask is whether it would be a bad idea to share a database between two web applications where both are querying and doing updates to the data. Will this slow down processing on the original site or possibly lock up data, etc.? Both sites would be running on the same machine...
TIA
If sharing of the same data between both application is important i.e. you want the data to be shared between applications - than you have to use the same database. It'll slow down processing, but if it's the requirement, then you have to.
There's nothing stopping you from having two applications accessing the database. They are built to have multiple connections with multiple people accessing them. So there aren't many risks involved. You probably won't even notice the speed difference.
The two biggest risks I can think of
if both applications edit a record in the database, the one that submitted data last will win unless you put business logic in place to prevent that from happening
if the database schema is updated, both applications need to be updated to reflect the new schema to let it access the new data, or edit the data successfully
I have made a django web app (postgresql backend) for internal use for one of my clients in New Zealand.
They have told me that they would also like it to be used by one of their branches in Malaysia (it will need to be connected to the same database). The problem is that apparently in Malaysia the internet is really unpredictable and there is a lot of downtime.
So here is the question, what would be the best way for keeping the Malaysian branch running when their internet is down and having their version of the database synchronised with the main database back here in NZ?
What you are trying to do is to synchronize your data and schema across multiple (2 in your case) postgresql databases.
There are a variety of solutions to do that depending on exactly what you want to achieve. This is a good place to start - http://www.postgresql.org/docs/devel/static/high-availability.html
and the summary of the different solutions and each solution's pros and cons are listed here -
http://www.postgresql.org/docs/devel/static/different-replication-solutions.html#HIGH-AVAILABILITY-MATRIX
I am new to servers and online databases, so please bear with me.
I have a question regarding database server communication on mobile devices as follows:
I am currently developing a game application on iOS. I have set up a non-SQL database on Cloudant and I would like to access that data on my iOS device. I have to update multiple database entries each time I complete a round, and I also need to read multiple entries on my database to refresh the leaderboard. I have tried to access multiple entries on Cloudant individually via device before, but most of them returned as timeout.
Thus, right now I have written several PHP scripts on my application server so that my device only needs to access the script once, and do multiple updates on my database or filter through the data I require from Cloudant. However, this means I need an additional server, meaning higher costs. I feel there should be a better or more elegant solution out there, and thus I would like to ask for help from everybody out here. Is it better to do all the updates directly from the device, or to enlist the help of a 3rd party?
Thanks for your time!
For security reasons alone it is necessary to use a server in front of the cloudant database. I assume you don't want every user of your app to be able to access the whole database. Also, the reasons you gave seem valid to me. It's generally a good idea to reduce the number and size of requests for a mobile application. Also, this might allow you to do some caching in the PHP server, ultimately reducing your costs.