A method, a system, and a computer program product for decompressing data. One or more compressed blocks in a set of stored compressed blocks responsive to a request to access data in the set of stored compressed blocks are identified. String prefixes inside the identified compressed blocks are decompressed using front coding. String suffixes inside the identified compressed blocks are decompressed using a re-pair decompression. Uncompressed data is generated.

A compression algorithm replaces duplicative strings with a copy pair indicating a location and length of a preceding identical string that is within a window from the duplicative string. Rather than a replacing a longest matching string within a window from a given point with a copy pair, the longest matching string may be used provide it is at least two bytes larger than the next longest matching string or is at a distance that is less than some multiple of a distance to the next longest matching string. In another aspect, the length of the window in which a matching string may be found is dependent on a length of the matching string. In yet another aspect, rather than labeling each literal and copy pair to indicate what it is, strings of non-duplicative literals are represented by a label and a length of the string.

A data compression device including a processor to perform a procedure comprising: obtaining data of a predetermined number (Z) of digits in a time series; and performing a compression process on the data. The data is obtained by encoding a vibration state of a measurement target. The compression process includes: deleting upper digits when the upper digits do not include significant information; and adding a unique code to a top of the upper digits when the upper digits include significant information. A digit number (X) of the upper digits is smaller than the predetermined number (Z).