Hi Bill, The following calculation based upon both the blocks allocated and the maximum record size seems to give a good mark count. Use the command "SHOW MARK" to display the mark count calculated below. ;+ ; ; CALMRK - Calculate the mark buffer record count. ; ; This routine calculates how often the record position should be marked. ; ; ((blocks_used * records/block)/mark_entrys) = mark_count. ; ; The worst case records/block is based upon the maximum record size. ; ; max_record > 256 use (512/32) = 16 records/block. ; max_record > 100 use (512/16) = 32 records/block. ; max_record > 32 use (512/8) = 64 records/block. ; max_record > 16 use (512/4) = 128 records/block. ; max_record < 16 use (512/2) = 256 records/block. ; ; The mark count is limited to a maximum of 50 records unless overridden. ; The calculation is overridden with the "/MARK=n" switch. ; ;-