A question came up in the InterSystems developer community concerning the possibility of creating a TWAIN interface to a Caché application. There were several great suggestions on how to get data from an imaging device on a web client to a server, then store this data in a database.
Some readers of my previous article, Caché eXTreme for .NET - direct access to globals from C#, wondered if you could access information not just from the same instance in which you’re working, but also from another instance on the same computer, or from an instance located on another computer in the same local network. Some theorized, correctly, that this would be possible using the Enterprise Cache Protocol (ECP). In this article I’m going to show how it can be done.
InterSystems states that Caché supports at least three data models – relational, object and hierarchical (globals). On can work with data presented in relational model in a program written on C# the same way one works with any other relational DB. To work with data presented by object model in C# one needs to use .NET Managed Provider or some kind or ORM. And starting with version 2012.2 one can work directly with globals (or use direct access to hierarchical data) via Caché eXTreme for .NET.
If you’ve ever wondered whether there is a way to regulate access to resources in Caché, wonder no more. In version 2014.2 special classes were added that allow developers to work with semaphores.
Recently I came across a very strong statement to the effect that InterSystems.Data.CacheClient.dll library works fast because it does not open a TCP/IP connection, instead it works in the same process as a database. It made me pause for quite some time. Firstly because .Net Managed Provider, which utilises this library, opens TCP/IP connection to the database (and it is stated in the documentation "Using .NET and the ADO.NET Managed Provider with Caché"). And secondly, because as far as I know only eXtreme applications attach themselves to the process. Besides, CacheClient for the most part