Well, if don't have access to GNU sort, you can always try one of the many other implementations of Unix sort.... ;-).

Anyway, you would do as Unix sort would do. Split up the data in sizes that you can swallow (how much that is depends from system to system). Sort that, and store it in a temporary file. Now you have a bunch of sorted files - and you have to merge them. You even might have to do this recursively.

Read Knuth if you want to know everything about merge sort.

Abigail