How did this work exactly? the program just never had to work on data greater than a certain statically known size? or did it process anything larger than that in chunks instead of mallocing a buffer of the necessary size?
Not necessarily. What this means, is you need to have a limit for every data structure in the application and have a strategy on how to either prevent the limit to ever be hit or how to deal when the limit is excercised.
Imagine a simple example of a webapp and number of user sessions.
Instead of the app throwing random errors or slowing down drastically, you could have a hard limit on the number of active sessions.
Whenever the app tries to allocate (find a slot) for a user session but it can't (all objects are already used), it will just throw an error.
This ensures that the application will always work correctly once you log in -- you will not experience a slowdown because too many users logged in.
Now, you also need to figure out what to do with users that received an error when trying to log in. They might receive an error and be told to log in later, they might be put on hold by UI and logged in automatically later or they might be redirected by loadbalancer to another server (maybe even started on demand).
When you start doing this for every aspect of application you get into situation where your application never really gets out of its design parameters and it is one of the important aspect to get an ultra stable operation.
Imagine a simple example of a webapp and number of user sessions.
Instead of the app throwing random errors or slowing down drastically, you could have a hard limit on the number of active sessions.
Whenever the app tries to allocate (find a slot) for a user session but it can't (all objects are already used), it will just throw an error.
This ensures that the application will always work correctly once you log in -- you will not experience a slowdown because too many users logged in.
Now, you also need to figure out what to do with users that received an error when trying to log in. They might receive an error and be told to log in later, they might be put on hold by UI and logged in automatically later or they might be redirected by loadbalancer to another server (maybe even started on demand).
When you start doing this for every aspect of application you get into situation where your application never really gets out of its design parameters and it is one of the important aspect to get an ultra stable operation.