ITS Instances
An Internet Transaction Server (ITS) installation consists of one or more ITS instances, each running one or more ITS services.
An ITS instance contains one or more AGate instances and one or more WGate instances. Each AGate instance may contain one or more AGate processes.
When you have run the ITS setup program once to create the physical installation, you can create any number of additional ITS instances on the same hardware by running it repeatedly.
Running multiple ITS instances as part of the same physical installation allows you to minimize hardware requirements.
The above graphic shows three ITS instances:
To install these 3 instances, you must run the ITS setup program three times.
In production systems, security is critical, so you need to be more careful:
In most cases, even in production systems, you only need to run one Web server and one WGate instance against one AGate instance, but larger or more complex setups are sometimes required. Below are some example configurations, which all assume that – in production systems at least – WGate and AGate are running on different machines.
Web Server – ITS Scalability
WGate Connects to Multiple AGate Processes
This configuration shows one Web server and a single WGate instance running against a single AGate instance that consists of multiple AGate processes. Multiple AGate processes allow you to handle large numbers of users, but you should take into account memory limitations.
Multiple Web Servers / WGates Connect to 1 AGate
This configuration shows multiple Web servers and WGate instances connected to a single AGate instance. This scenario may be useful if you want to set up separate Web servers for Internet and intranet users.
Multiple ITS Instances Connect to the Same R/3 System
This configuration shows multiple Web servers and WGate instances, each connected to a separate AGate instance, but all pointing to the same R/3 application server. You would need to establish that the application server can handle the additional load of all the ITS instances. This scenario is not very likely in production environments, but it could be appropriate for development environments.
WGate – AGate Load Balancing
From Release 4.6D, the ITS supports load balancing by allowing you to attach several AGate instances – each running on a separate machine – to the same Web server and WGate instance, or to multiple Web servers.
Single WGate Interconnects With Multiple AGates
This configuration reduces the risk of failure in large scale implementations. The WGate takes the capacity of each AGate instance into account, but there is a random element in the selection of the AGate instance to which the request is to be routed.
Multiple WGates Interconnect With Multiple AGates for High Availability Systems
This configuration reduces the risk of failure in large scale implementations even further, because requests can be routed through any WGate instance. You cannot know in advance how requests are going to be routed, so it is essential that all WGates are connected to all AGates.
ITS – R/3 Scalability
ITS Connects to Single R/3 Application Server
ITS Connects to R/3 Message Server for Load Balancing
The ITS benefits from R/3 scalability through:
Buffering database tables on the application server achieves faster access to data.