1. A method of storing data in a memory, the data being captured from a digital communications network, for processing by a processing unit that accesses the memory and executes computer executable instructions, said captured data comprising a stream of messages having message parameters, said stream of messages comprising messages of a plurality of communications sessions, the method comprising: inputting data from said stream of messages; writing, for sequential ones of said stream of messages, sequential sets of parameters into a first FIFO (first-in first out) data structure, at an entry point of said first FIFO data structure; reading said sequential sets of parameters from an exit point of said first FIFO data structure; and writing said sequential sets of parameters read from said first FIFO data structure into a second data structure; and wherein said entry point and said exit point are separated by a first data structure length; and wherein said first data structure length has a predetermined minimum value when a set of parameters of said sequential sets of parameters is read from said exit point, wherein said predetermined minimum value is defined in terms of a plural number of said sets of parameters and/or in terms of a time between writing of one of said sets of parameters into said first data structure at said entry point of said first FIFO data structure and reading of a set of parameters of said sequential sets of parameters from said exit point of said first data structure, said time sufficient to write sets of parameters successively into said first FIFO data structure.