Heap File Organization Records can be placed anywhere in the file where there is free space Records usually do not move once allocated Important to be able to efficiently find free space within file ■Free-space map Array with 1 entry per block.Each entry is a few bits to a byte,and records fraction of block that is free In example below,3 bits per block,value divided by 8 indicates fraction of block that is free 4214736512011056 Can have second-level free-space map In example below,each entry stores maximum from 4 entries of first- level free-space map 4726 Free space map written to disk periodically,OK to have wrong (old)values for some entries(will be detected and fixed) Database System Concepts-7th Edition 13.11 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 13.11 ©Silberschatz, Korth and Sudarshan th Edition Heap File Organization ▪ Records can be placed anywhere in the file where there is free space ▪ Records usually do not move once allocated ▪ Important to be able to efficiently find free space within file ▪ Free-space map • Array with 1 entry per block. Each entry is a few bits to a byte, and records fraction of block that is free • In example below, 3 bits per block, value divided by 8 indicates fraction of block that is free • Can have second-level free-space map • In example below, each entry stores maximum from 4 entries of first￾level free-space map ▪ Free space map written to disk periodically, OK to have wrong (old) values for some entries (will be detected and fixed)