The size of the matrix buffer and the number of records which are stored there can be specified for the compression procedure using the maxbuffer and maxrecords parameters. As a general rule, the efficiency of the compression procedure increases the more records are compressed together in the same block. If there are no other factors which need to be taken into account, it is normally best to choose the highest possible number (255 or 4095, resp.). This preset number is, however, merely an upper limit. There may be fewer records if the space in the matrix buffer is exhausted or if the end of the original file is reached.
The size which must be set for the matrix buffer is dependent on the number and size of the records that need to be buffered.The space requirement for files with fixed-size records is calculated simply as the product of the number of records and the record size. If the files have a variable record size, it is not normally possible to predict the memory requirement exactly. The value which is chosen is bound to be approximate. However, the matrix buffer must always be at least large enough to hold every individual record in the file.