IBM DS8000 manual Path group identifier, Physical path, Pinned data, Point-in-time copy

associating multiple devices of a single control-unit image with a single logical device. Up to eight device addresses can be assigned to a PAV. The PAV function enables two or more concurrent write operations to the same logical volume, as long as the write operations are not to the same extents. See also extent, I/O Priority Queueing, and multiple allegiance.

parity A data checking scheme used in a computer system to ensure the integrity of the data. The RAID implementation uses parity to re-create data if a disk drive fails.

path group

In zSeries architecture, a set of channel paths that are defined to a control unit as being associated with a single logical partition (LPAR). The channel paths are in a group state and are online to the host. See also logical partition.

path group identifier

In zSeries architecture, the identifier that uniquely identifies a given logical partition (LPAR). The path group identifier is used in communication between the LPAR program and a device. The identifier associates the path group with one or more channel paths, thereby defining these paths to the control unit as being associated with the same LPAR. See also logical partition.

PAV See parallel access volume.

PCI See peripheral component interconnect. PDU See protocol data unit.

PE See IBM product engineering.

peripheral component interconnect (PCI) An architecture for a system bus and associated protocols that supports attachments of adapter cards to a system backplane.

persistent FlashCopy

A state where a FlashCopy relationship remains indefinitely until the user deletes it. The relationship between the source and target volumes is maintained after a background copy completes.

physical path

A single path through the I/O interconnection fabric that attaches two units. For Copy Services, this is the path from a host adapter on one DS8000

(through cabling and switches) to a host adapter on anotherDS8000.

pinned data

Data that is held in cache until either an error condition is corrected and it can be moved to disk storage or until the data is discarded by a host command. Pinned data conditions can only occur on an ESS Model 800 during fast-write or dual-copy functions.

point-in-time copy

A FlashCopy option that creates an instantaneous view of original source data at a specific moment in time.

point-to-point connection

A fibre-channel topology that enables the direct interconnection of ports. See also arbitrated loop and switched fabric.

port A physical connection on a host adapter to the cable that connects the DS8000 to hosts, switches, or another DS8000. The DS8000 uses SCSI and ESCON host adapters that have two ports per adapter, and fibre-channel host adapters that have one port. See also ESCON, fibre channel, host adapter, and small computer system interface.

POST See power-on self test.

power-on self test (POST)

A diagnostic test that servers or computers run when they are turned on.

predictable write

A write operation that can cache without knowledge of the existing format on the medium. All write operations on FBA DASD devices are predictable. On CKD DASD devices, a write operation is predictable if it does a format write operation for the first data record on the track.

primary control unit

The DS8000 to which a Remote Mirror and Copy primary device is physically attached.

processor complex

A partition of a storage server that is capable of performing all defined functions of the storage server. Multiple processor complexes provide redundancy.

product engineering

See IBM product engineering.

344IBM TotalStorage DS8000: Messages Reference