P

package

A control structure produced during program preparation that is used to execute SQL statements.

page

(1) A block of storage within a table or index whose size is 4096 bytes (4KB).

(2) A unit of storage within a table space (4KB, 8KB, 16KB, or 32KB) or index space (4KB). In a table space, a page contains one or more rows in a table. In a LOB table space, a LOB value can span more than one page, but no more than one LOB value is stored on a page.

parallelism

The ability to perform multiple database operations at the same time.

parameter marker

A question mark (?) that appears in a statement string of a dynamic SQL statement. The question mark can appear where a host variable might appear if the statement string was a static SQL statement.

parameter name

A long identifier naming a parameter that can be referenced in a procedure or user-defined function.

parent key

A primary key or unique key that is used in a referential constraint. The values of a parent key determine the valid values of the foreign key in the constraint.

parent row

A row that has at least one dependent row.

parent table

A table that is a parent in at least one referential constraint.

partitioned database

A database with two or more database partitions. Each database partition stores a subset of table data for each table that resides on it.

partitioning key

An ordered set of one or more columns in a given table. For each row in the table, the values in the partitioning key columns determine on which database partition the row belongs.

partitioning map

A vector of partition numbers that maps a partitioning map index to database partitions in the database partition group.

partitioning map index

A number that is assigned to a hash partition or range partition.

path

(1) In an operating system, the route through a file system to a specific file.

(2) In a network environment, the route between any two nodes.

PC version of Integrated Exchange Format (PC/IXF)

IXF data interchange architecture is a generic relational database exchange format that lets you move data among DB2 databases.

performance snapshot

Performance data for a set of database objects that is retrieved from the database manager at a point in time.

phantom row

A table row that can be read by application processes executing with any isolation level except repeatable read. When an application process issues the same query multiple times within a single unit of work, additional rows can appear between queries because of the data being inserted and committed by application processes that are running concurrently.

plug-in

A dynamically loadable library that DB2 UDB uses to carry out user-written actions that involve the database.

point of consistency

A point in time when all the recoverable data that a program accesses is consistent. The point of consistency occurs when updates, insertions, and deletions are either committed to the physical database or rolled back.

precision

In numeric data types, the total number of binary or decimal digits, excluding the sign. The sign is considered positive if the value of a number is zero.

precompile

To process programs that contain SQL statements before they are compiled. SQL statements are replaced with statements that will be recognized by the host language compiler. The output from a precompile process includes source code that can be submitted to the compiler and used in the bind process.

predicate

An element of a search condition that expresses or implies a comparison operation.

prefetching

Prefetching pages means that one or more pages are retrieved from disk in the expectation that they will be required by an application. Prefetching index and data pages into the buffer pool can help improve performance by reducing the I/O wait time. In addition, parallel I/O enhances prefetching efficiency.

prepare

(1) To convert an SQL statement from text form to an executable form by submitting it to the SQL compiler.

(2) The first phase of a two-phase commit process in which all participants are requested to prepare for commit.

prepared SQL statement

In SQL, a named object that is the executable form of an SQL statement processed by the PREPARE statement.

primary database

In High Availability Disaster Recovery (HADR), the main database, which is accessed by applications. Applications apply updates to the primary database, and those updates are propagated on the standby database by using log shipping.

primary key

A unique key that is part of the definition of a table. A primary key is the default parent key of a referential constraint definition. It is a column or combination of columns that uniquely identifies a row in a table.

primary log

A set of one or more log files used to record changes to a database. Storage for these files is allocated in advance.

principal

An entity that can communicate securely with another entity. In Kerberos, principals are represented as entries in the Kerberos registry database and include users, servers, computers, and others.

private memory

Memory allocated for a program/process when that process is performing work. This memory is only accessible by the program or process that allocated it.

privilege

The right to access a specific database object in a specific way. Privileges are controlled by users with SYSADM (system administrator) authority, DBADM (database administrator) authority, and by creators of objects. For example, privileges include rights to create, delete, and retrieve data from tables.

procedure

See [stored procedure]

pseudo deleted

A key that is marked as deleted but has not yet been physically removed from the index page.

public authority

The authority for an object granted to all users.