72. A system as defined in claim 71, wherein the interrogation data characteristic statistics generated by the interrogation processor include a frequency distribution of characters found in the scanned record, a rate of occurrence for each character in the frequency distribution, and an entropy value of the scanned record; and the interrogation processor further comprises: means for completing a stabilization procedure comprising repeating the steps of selecting a current record block for scanning and generating a current set of the interrogation statistics, selecting a new record block, different from the current block, for scanning and generating a new set of the interrogation statistics, and comparing like statistics of the current set of statistics and the new set of statistics, until the difference between the like statistics is below a predetermined stabilization threshold value or the number of scanned record blocks equals a predetermined scanning limit value, and thereupon storing the new block in an interrogation buffer and storing the set of new interrogation statistics in the memory if the entropy value is below a predetermined entropy threshold value.
71. A computer system comprising: a central processing unit including a data compression facility and a file access method interface; one or more users that communicate with the central processing unit; one or more applications that are controlled by the users and generate uninterrupted byte strings of datasets; external data storage devices that receive data sets from the file access method interface; memory containing data catalogs having information identifying the format of each data set and its location in external storage, the data sets comprising records of byte strings and assuming either a closed status in which the data set cannot be accessed or an open status in which the data set is subject to access commands; a library of dictionary segments that are adapted for use by the central processing unit to create a Ziv-Lempel tree for the data compression facility; an interrogation processor that initiates scanning the records during an initial recordation of a data set to the external storage and generating predetermined interrogation data characteristic statistics for selecting dictionary segments according to the generated interrogation statistics and either combining the selected dictionary segments to form a system-built dictionary or designating one or more dictionary segments for a sampling process; and a sampling processor that retrieves designated sample byte strings from the records and scans the sample byte strings with the dictionary segments designated by the interrogation processor to generate predetermined sampling statistics, wherein the interrogation processor and sampling processor designate the selected dictionary segments with a dictionary identifier representing each dictionary segment and the combination further comprises: a dictionary build processor that receives the dictionary identifiers representing the dictionary segments of the system-built dictionary and retrieves the corresponding dictionary segments from the library upon the data set being opened to create the system built dictionary for use during future access commands; an access method processor that stores the dictionary identifiers in the system data catalog upon the data set being closed and retrieves the identifiers upon the data set being opened; and a process router that controls the operation of the combination to initiate operation of either the interrogation processor, the sampling processor, the access method processor, or the dictionary build processor.