2.3.1 HN (Heap-on-Node)
The Heap-on-Node defines a standard heap over a node's data stream. Taking advantage of the flexible structure of the node, the organization of the heap data can take on several forms, depending on how much data is stored in the heap.
For heaps whose size exceed the amount of data that can fit in one data block, the first data block in the HN contains a full header record and a trailer record. With the exception of blocks that require an HNBITMAPHDR structure, subsequent data blocks only have an abridged header and a trailer. This is explained in more detail in the following sections. Because the heap is a structure that is defined at a higher layer than the NDB, the heap structures are written to the external data sections of data blocks and do not use any information from the data block's NDB structure.