A
file structure where all data is contained in data blocks and a
B+Tree indexes into the data blocks. The B+Tree,
which consists of nodes, is maintained internally by the TPFDF product.
The nodes consist of one root node, internal nodes, and leaf nodes. The
root and internal nodes point to other nodes, and the leaf nodes point to data
blocks. The B+Tree is dynamically balanced so that the
B+Tree is of uniform depth. See also root node,
internal node, and leaf node.
basic indexing
A method of creating TPFDF
structures that include index and detail files.
block
A physical storage area used by the
TPFDF product that contains a header, logical records (LRECs), and an optional
trailer. (A block is the TPFDF term for a TPF or ALCS record.)
block header
The standard header in data
blocks (records) that includes information such as the file ID, the record
code check (RCC), data control, program name, and chaining address
fields. The block header for TPFDF blocks includes all fields in the
standard TPF and ALCS header plus additional fields used only for the TPFDF
product.
block index support
A method that the TPFDF
product uses to identify which logical records (LRECs) are contained in
overflow blocks of a subfile. Block index support allows faster access
to LRECs in overflow blocks. This support only works if the LRECs are
organized UP (ascending) or DOWN (descending) in each subfile.
block trailer
An optional area located at
the end of each TPFDF block that contains information about the block.