My app reads data from two sources, a local sqlite file and a remote server which is a clone of the local db but with lots of pictures. I do not write to the server database, but I do need multiple simultaneous fetch operations.
What DBMS should I use for storing information on the server?
It needs to be very easily used from an iPhone app, be reliable, etc.
Talking to a remote server should not be tied to any platform like iOS. If you have control over the remote db server, the best bet IMO is crafting a RESTful API which you express your queries in, the server processes it and sends you the pictures/records using proper content type. If you do NOT have such control over the remote db, you’ll have to stick to the API the db hoster provides. There are plenty such “on the cloud” db hosters (including NoSQL solutions) that give you a web-services interface to your db. MongoLabs is one such provider for MongoDB(which is a NOSQL db – meaning no schemas, no bounds on the structure of a “table”). You can continue to stick to SQLite on the client side.