A TPFDF operation that reduces the
number of blocks used to hold logical records (LRECs) contained in a
subfile. A pack operation is initiated by the TPFDF product when any
LREC has been deleted and the number of LRECs in any block falls below a
threshold defined in the DSECT macro or DBDEF macro for the file. The
number of LRECs placed in each block is also controlled by the DSECT or DBDEF
macro. A pack operation can also be initiated by an application program
when the subfile is closed, or by the ZUDFM or ZFCRU commands.
parameter table
The source of parameter
values that define how a capture/restore utility, information and statistics
environment (CRUISE) function is processed.
parametric recoup
The attribute of the file
recoup program that allows the program to be activated and controlled by
parameter lists.
parent node
In a B+Tree index, a
node that produces and points to a lower-level child node. See also
child node and sibling node.
partitioned file
A file where the prime
blocks are grouped together into different partitions. Each partition
has the same number of subfiles. The prime blocks of the different
partitions follow each other sequentially on DASD. For example, if
there are three partitions (A, B, C), and each contains four prime blocks, the
prime blocks occur in the sequence: A1, A2, A3, A4; B1, B2, B3,
B4; C1, C2, C3, C4. You can easily increase the number of
partitions by increasing the size of the file. You cannot easily
increase the number of prime blocks.
path
A means of referencing a detail file or
intermediate index file from an index file. Each different reference is
identified by a path number (0, 1, 2, ...) defined by the database
administrator. See also update path and read-only
path.
pool file
A TPFDF file where the prime block
is contained in a TPF or ALCS pool record. Typically, pool files are
used for detail files or intermediate index files. Contrast with
fixed file.
primary key
Synonym for LREC
ID.
prime block
The first block in the chain of
blocks that comprise a subfile. All other blocks are referred to as
overflow blocks. The subfile can contain zero or more overflow
blocks. The prime block is either a fixed file or pool record.
See also fixed file, pool file, and overflow
block.
pushdown chaining
A file in which records
are always added to the prime block of the subfile. If there is not
enough room, the logical records (LRECs) in the prime block are moved to a new
overflow block, the prime block is initialized, and the LREC added. A
pushdown chaining file is indicated by bit 3 of symbol &SW00OP1 in the
DSECT of the file.