I'm glad you posted this. I'm running a similar app, ie reading many rows of data into a complex data structure then manipulating the data as a whole, and the problem definately is in the memory de-allocation (I'm running this app on W2K). According to the task manager the app has 534MB RAM allocated to it (all but a small proportion of it to the one, main, data structure). Trying to free the memory ($hash->{head} = ();) results in the disk light coming on and that's about it. It's currently generating 90 page faults a second, and is approaching 500K page faults in total. Not bad for a data structure that took less than 10 minutes to build.

rdfield