Hi Art,

One IceCap session is consuming, exactly the same resources that a normal 5250 application do. However, you are more easy let into start more session in IceCap that you will do with Client Access because IceCap starts new sessions when you add new tabs to your work panel. So one tab in IceCap maps one-to-one with a session window in Client Access. On top of that all IceCap session is encapsulated into one IceBreak job, which again is super lightweight. Does it sound cryptic? Well it is not; let me explain:

When you bring the 5250 to the web you need some mechanism to keep the HTTP protocol alive. This is where IceBreak comes in. IceBreak it self has proven it is the most resource effective server on the market beating Apache/GCI with a 1:6 ratio and Apache/PHP with 1:10 and WAS with at ratio from 1:30 to 1:100 depending how well WAS is tuned.

But no matter how we twist or turn it it will use some kind of resources: And web resources are not cheap compared to 5250 when it comes to I.e. graphics  any picture, icon, table, sheet, flash movie, gif, png, html file has no counter part in the 5250. So at the end of the day the workload of you AS/400 will increase. But let me give you some figures from the real life:

U.K. Largest entrepreneur companyGrahams Systems are using IceBreak  http://www.graham.co.uk/. They stated the project on a AS/400 model 250, and it handled up to 2000 users at a time. Well; the design off the application was quite clever and did actually encapsulate some old S/36 applications. And since S/36 apps had a extremely little footprint, it was possible to run that on such a little box. Now with the growth of the success of using AS/400 technology that have purchased a 515 and have no performance issues what so ever.

But with more possibilities comes more requirements to the system. The new enhancements to the applications is also driving piecharts, sheets, tables, queries etc. So the 515 are not "sleeping" any longer.

One thing to have in mind with Grahams is – they have converted everything to IceBreak RPG, so they have no IceCap'ed 5250 applications left. Otherwise it will not have been possible to run 2000 user on a 250.

Now back again to your case.
If you just move you application to IceCap and run it there, you will only expect a 2-5% more CPU requirements. So if your CPU utilization is around 80% it is time to upgrade. Remember you are now ALSO running an web-server / application-server on you IBMi.  Now – If you rewrite some of you mission critical apps to be real IceBreak programs you can get rid of the 5250 penalty and it will REDUCE the all over requirement for CPU and have a possibility to a new features and modern functionality to your application.
 
The next thing you will consider: Now you have the IceBreak webserver running – why not make it available to the internet, and bring customers, clients, partners into you system? And this is what I mean with " with more possibilities comes more requirements to the system". If you are looking at a know number of – lets say 2000 users. The numbers are more or less not predictable when you open you system to the web. However, this is a reflection of "good news" to you CEO – You are bringing more services to you business associates, which again makes the business more efficient – and yes it comes with at price: system upgrades…
 
The price of software:
Remember that IceCap is priced pr. seat and IceBreak is priced pr. Box - not LPAR. You can run as many IceBreak servers in as many subsystems in as many LPAR's you like for the same price.

Best regards,
Niels Liisberg