My company has Desktop application developed in vb.net using devexpress controls. Back End database is MySQL.

Company is in retailing and have 2 retail stores in in same city. Both stores always stay busy and customers are always in waiting at the counter. Basically, it is desktop based CRM application which has lot of modules inside it apart from invoice/Receipt module, it has other modules like Delivery module, installation module, Service/Repair module, Account Receivable module and many other modules used by various back office departments of the company. Other resources/hardware such as Barcode Printer, Receipt Printer, and Barcode scanner are connected to the CRM on Desktop PC.

Currently, there are around 55 clients always connected to server and using application.

Problem:

Till couple of weeks back, company had no issue using this desktop application and single MySQL server as all clients were connected via LAN or WLAN.

Now situation has changed, and new requirement has raised: Company has planned to open new stores at very far distance. Such stores cannot be connected to current central database via LAN or WLAN. Each new branch would have around 20-30 clients, say “Branch Clients”

Also, there would be field executive who will be working from their laptop. Say “Remote Clients”. They will just have 3G internet connection on their laptop.

Thought 1: Install desktop application at all branch PCs, and connect them to central MySQL database server over the internet.

Not possible: Connection over the internet would be very slow for fetching such huge data. Data is really huge For, e.g. if client opens “Customer Master”, then there would be more than 600,000 rows which takes lot of bandwidth and time to open over the internet. And there are many more such modules which loads lot of data.

Also, in case of losing internet connection, clients would not able to operate the application. Customer waiting in line to make receipt would go crazy if they have to wait for long.

Thought 2: Install new MySQL server at branch store, all the desktop PCs then would be connected to that local branch server. And then that local branch server would be connected to central server via MySQL replication option.

Not possible: Since MySQL replication has limitation of only one way replication, we cannot implement this structure. Application requires to move data from central server to branch server and from Branch to Central in real-time. Also, MySQL replication engineering has limitation to replicate only with one server only. In that case, we cannot replicate with multiple branch stores. There is an option of cluster server, but company cannot afford licensing cost.

Thought 3: Somebody suggested me that I should transfer entire desktop application into Web Application and get cloud server for database.

Not possible: I think looking at current requirement (fast access), environment (retail store-pos) and hardware (printers, scanners) connected to client - it is not advisable to have web application and cloud database server. Also in the event of no internet, entire store would go down.

Thought 4: Somebody suggested me that I should move from MySQL server to MSSQL and keep desktop application as it is. MSSQL has capability to sync with multiple servers in real-time over the internet. It has no limitation like MySQL’s one way replication and only one replication connection.

I guess, to make faster and constant database connection, installing local branch server is highly required. But I don’t know how those different branch servers could be connected to central server.

My Questions:

• What is the best way to resolve above issues in given condition and successfully fulfill the company’s requirement? Faster and constant connection to database server. And also real-time updates between all branches and central server. If internet connection is down, then delay in real-time update is acceptable but clients should not be affected from work.

• Would migration from MySQL to MSSQL resolve the issue? Because data migration is not issue as there are many tools available which converts the database from one platform to other. But issue is - application is very huge having hundreds of query written for MySQL. I guess I have to change those all queries also, because queries are not same for MySQL and MSSQL. Do I have to change all the queries or just the few percentage queries? Or if there is any tool available which convert queries from MySQL to MSSQL query.

• In general, how such small-medium retail store company have their infrastructure and application setup? Let me know some ideas.