Glossary
A
AOM. Asynchronous operations manager.
application system. A system made up of one or more host systems that perform the main set of functions for an establishment. This is the system that updates the primary disk volumes that are being copied by a copy services function.
asynchronous operation. A type of operation in which the remote copy XRC function copies updates to the secondary volume of an XRC pair at some time after the primary volume is updated. Contrast with synchronous operation.
B
backup. The process of creating a copy of data to ensure against accidental loss.
C
cache. A random access electronic storage in selected storage controls used to retain frequently used data for faster access by the channel.
central processor complex (CPC). The unit within a cluster that provides the management function for the storage server. It consists of cluster processors, cluster memory, and related logic.
channel connection address (CCA). The input/output (I/O) address that uniquely identifies an I/O device to the channel during an I/O operation.
channel interface. The circuitry in a storage control that attaches storage paths to a host channel.
consistency group time. The time, expressed as a primary application system time-of-day (TOD) value, to which XRC secondary volumes have been updated. This term was previously referred to as “consistency time”.
consistent copy. A copy of a data entity (for example a logical volume) that contains the contents of the entire data entity from a single instant in time.
control unit address. The high order bits of the storage control address, used to identify the storage control to the host system.
D
dark fibre. A dedicated fibre link between two sites that is dedicated to use by one client.
DASD. direct access storage device.
data in transit. The update data on application system DASD volumes that is being sent to the recovery system for writing to DASD volumes on the recovery system.
data mover. See system data mover.
device address. The ESA/390 term for the field of an ESCON device-level frame that selects a specific device on a control unit image. The one or two leftmost digits are the address of the channel to which the device is attached. The two rightmost digits represent the unit address.
device number. The ESA/390 term for a four-hexadecimal-character identifier, for example 13A0, that you associate with a device to facilitate communication between the program and the host operator. The device number that you associate with a subchannel.
Device Support Facilities program (ICKDSF). A program used to initialize DASD at installation and perform media maintenance.
DFDSS. Data Facility Data Set Services.
DFSMSdss. A functional component of DFSMS/MVS used to copy, dump, move, and restore data sets and volumes.
Disaster Recovery. Recovery after a disaster, such as a fire, that destroys or otherwise disables a system. Disaster Recovery techniques typically involve restoring data to a second (recovery) system, then using the recovery system in place of the destroyed or disabled application system. See also recovery, backup, and recovery system.
dual copy. A high availability function made possible by the nonvolatile storage in cached IBM storage controls. Dual copy maintains two functionally identical copies of designated DASD volumes in the logical storage subsystem, and automatically updates both copies every time a write operation is issued to the dual copy logical volume.
duplex pair. A volume composed of two physical devices within the same or different storage subsystems that are defined as a pair by a dual copy, PPRC, or XRC operation, and are not in suspended or pending state. The operation records the same data onto each volume.
DWDM. Dense Wavelength Division Multiplexor. A technique used to transmit several independent bit streams over a single fiber link.
E
extended remote copy (XRC). A hardware- and software-based remote copy service option that provides an asynchronous volume copy across storage subsystems for Disaster Recovery, device migration, and workload migration.
F
fixed utility volume. A simplex volume assigned by the storage administrator to a logical storage subsystem to serve as working storage for XRC functions on that storage subsystem.
FlashCopy A point-in-time copy services function that can quickly copy data from a source location to a target location.
floating utility volume. Any volume of a pool of simplex volumes assigned by the storage administrator to a logical storage subsystem to serve as dynamic storage for XRC functions on that storage subsystem.
J
JCL. Job Control Language.
journal. A checkpoint data set that contains work to be done. For XRC, the work to be done consists of all changed records from the primary volumes. Changed records are collected and formed into a “consistency group”, and then the group of updates is applied to the secondary volumes.
K
km. kilometer.
L
Licensed Internal Code (LIC). Microcode that IBM does not sell as part of a machine, but licenses to the customer. LIC is implemented in a part of storage that is not addressable by user programs. Some IBM products use it to implement functions as an alternative to hard-wired circuitry.
link address. On an ESCON interface, the portion of a source or destination address in a frame that ESCON uses to route a frame through an ESCON director. ESCON associates the link address with a specific switch port that is on the ESCON director. Equivalently, it associates the link address with the channel subsystem or controller link-level functions that are attached to the switch port.
logical partition (LPAR). The ESA/390 term for a set of functions that create the programming environment that is defined by the ESA/390 architecture. ESA/390 architecture uses this term when more than one LPAR is established on a processor. An LPAR is conceptually similar to a virtual machine environment except that the LPAR is a function of the processor. Also, the LPAR does not depend on an operating system to create the virtual machine environment.
logical subsystem. The logical functions of a storage controller that allow one or more host I/O interfaces to access a set of devices. The controller aggregates the devices according to the addressing mechanisms of the associated I/O interfaces. One or more logical subsystems exist on a storage controller. In general, the controller associates a given set of devices with only one logical subsystem.
LSS. See logical subsystem.
O
orphan data. Data that occurs between the last, safe backup for a recovery system and the time when the application system experiences a disaster. This data is lost when either the application system becomes available for use or when the recovery system is used in place of the application system.
P
peer-to-peer remote copy. A hardware-based remote copy option that provides a synchronous volume copy across storage subsystems for Disaster Recovery, device migration, and workload migration.
pending. The initial state of a defined volume pair, before it becomes a duplex pair. During this state, the contents of the primary volume are copied to the secondary volume.
PPRC. Peer-to-peer remote copy.
PPRC dynamic address switching (P/DAS). A software function that provides the ability to dynamically redirect all application I/O from one PPRC volume to another PPRC volume.
primary device. One device of a dual copy or remote copy volume pair. All channel commands to the copy logical volume are directed to the primary device. The data on the primary device is duplicated on the secondary device. See also secondary device.
PTF. Program temporary fix.
R
RACF. Resource Access Control Facility.
recovery system. A system that is used in place of a primary application system that is no longer available for use. Data from the application system must be available for use on the recovery system. This is usually accomplished through backup and recovery techniques, or through various DASD copying techniques, such as remote copy.
remote copy. A storage-based Disaster Recovery and workload migration function that can copy data in real time to a remote location. Two options of remote copy are available. See peer-to-peer remote copy and extended remote copy.
resynchronization. A track image copy from the primary volume to the secondary volume of only the tracks that have changed since the volume was last in duplex mode.
S
secondary device. One of the devices in a dual copy or remote copy logical volume pair that contains a duplicate of the data on the primary device. Unlike the primary device, the secondary device may only accept a limited subset of channel commands.
sidefile. A storage area used to maintain copies of tracks within a concurrent copy domain. A concurrent copy operation maintains a sidefile in storage control cache and another in processor storage.
simplex state. A volume is in the simplex state if it is not part of a dual copy or a remote copy volume pair. Ending a volume pair returns the two devices to the simplex state. In this case, there is no longer any capability for either automatic updates of the secondary device or for logging changes, as would be the case in a suspended state.
site table. Entity within GDPS that is created from information in the GEOPLEX DOMAINS. It contains a list of all the systems in the GDPS environment.
suspended state. When only one of the devices in a dual copy or remote copy volume pair is being updated because of either a permanent error condition or an authorized user command. All writes to the remaining functional device are logged. This allows for automatic resynchronization of both volumes when the volume pair is reset to the active duplex state.
synchronization. An initial volume copy. This is a track image copy of each primary track on the volume to the secondary volume.
synchronous operation. A type of operation in which the remote copy PPRC function copies updates to the secondary volume of a PPRC pair at the same time that the primary volume is updated. Contrast with asynchronous operation.
system data mover. A system that interacts with storage controls that have attached XRC primary volumes. The system data mover copies updates made to the XRC primary volumes to a set of XRC-managed secondary volumes.
T
timeout. The time in seconds that the storage control remains in a “long busy” condition before physical sessions are ended.
U
utility volume. A volume that is available to be used by the extended remote copy function to perform data mover I/O for a primary site storage control’s XRC-related data.A device that is used to gather information about the environment for configuration setup. It is also used to issue PPRC Freeze commands to the SSID-pair.
 
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