4.6 Data block

Default data block size is 1MiB ( 1048576 bytes, 256 pages on ix86 ). This value can be altered during creation of file See Block size. ( and may be resized later - currently unsupported)

A data block contains following sections :

• Block header and the bases of three independent AVL trees :
• Records tree ( of user-defined data )
• Block free-list by address
• Block free-list by size

All three trees in datablock lives in common address space - when the data block is empty records tree has no nodes, free-list by address and free-list by size have one common node with address after block header and size equal block size - block header.

Each node (struct) of the AVL tree, e.g. struct in C, has to begin with two items:

• adb_magic_t magic ;
• adb_tavl_node_t node ;
• Fixed part of record, described in meta-scheme
• Variable part(s) of record, described in fixed part