We describe techniques for storing and processing data captured in large volumes from digital mobile phone networks. One technique inputs a stream of messages, writes sequential sets of message parameters into a first FIFO at an entry point; reads the parameters from an exit point; and writes the read parameters into a second data structure. Importantly in this technique the entry point and the exit point are separated by predetermined minimum length defined in terms of a number of the sets of parameters and/or a time. Some preferred implementations also include a last value data store or bucket to store one or more most recent previous values of message parameters.