As you work with independent disk pools, you need to become familiar with the following terms. For more terms and concepts, you can access the information center glossary.
Important: The terms independent auxiliary storage pool (ASP) and independent disk pool are synonymous.
- active state
- In geographic mirroring, pertaining to the configuration state of a mirror copy that indicates geographic mirroring is being performed if the disk pool is available.
- asynchronous
- In geographic mirroring, pertaining to the mode where the program issuing the update waits until the operation is completed on the production copy and received for processing on the target system.
- cluster
- A collection of complete systems that work together to provide a single, unified computing capability. An iSeries™ cluster is made up of only iSeries servers and is required when implementing switchable independent disk pools.
- cluster resource group (CRG)
- A collection of related cluster resources that defines actions to be taken during a switchover or failover operation of the access point of resilient resources. These resilient resources include applications, data, and devices. The group describes a recovery domain and supplies the name of the cluster resource group exit program that manages the movement of an access point. A device CRG contains a list of devices, such as independent disk pools. The independent disk pools can reside on a switchable entity that can be either an expansion unit (frame/unit) or an IOP. In iSeries Navigator, a device cluster resource group is referred to as a switchable hardware group.
- cross-site mirroring (XSM)
- A feature of i5/OS™ High Available Switchable Resources (Option 41) that provides geographic mirroring and the services to switch over or automatically cause a failover to a mirror copy, potentially at another location, in the event of an outage at the primary location.
- data port services
- The generic transport mechanism used by geographic mirroring to send updates from the source system that owns the production copy to the target system that owns the mirror copy.
- detach
- In geographic mirroring, to disassociate a mirror copy from the production copy in order to use the mirror copy for a separate operation, such as to save data, to run reports, or to perform data mining. Detaching a mirror copy suspends geographic mirroring.
- detached mirror copy
- A detached mirror copy of an independent disk pool is a mirror copy that is disassociated from the production copy in a geographic mirroring environment.
- device description
- An object that contains information describing a particular device or logical unit (LU) that is attached to the system. A device description is a description of the logical connection between two LUs (local and remote locations). The system-recognized identifier for the object type is *DEVD.
- device domain
- A device domain is a collection of cluster nodes that share device resources, such as independent disk pools. For independent disk pools, the resources are: virtual addresses, disk pool numbers and disk unit numbers. An independent disk pool can only be accessed by the nodes in one device domain.
- disk pool
- An auxiliary storage pool that contains only disk units.
- disk pool group
- Made up of a primary disk pool and zero or more secondary disk pools, each of which are independent in regard to data storage, but combine to act as one entity.
- disk unit
- A physical enclosure containing one or more disk drives.
- expansion unit
- A feature that can be connected to a system unit to provide additional storage and processing capacity.
- failover
- A cluster event where the primary database server or application server switches over to a backup system due to the failure of the primary server
- geographic mirroring
- A subfunction of cross-site mirroring (XSM) that generates a mirror image of an independent disk pool on a system, which is (optionally) geographically distant from the originating site for availability or protection purposes.
- HSL (high-speed link) loop
- The system-to-expansion unit connectivity technology that is required to use switchable independent disk pools residing on an expansion unit (frame/unit). The servers and expansion unit in a cluster using resilient devices on an external expansion unit must be on an HSL loop connected with HSL cables.
- independent disk pool
- Disk pools 33 to 255. One or more storage units that are defined from the disk units or disk-unit subsystems that make up addressable disk storage. An independent disk pool contains objects, the directories and libraries that contain the objects, and other object attributes such as authorization ownership attributes. An independent disk pool can be made available (varied on) and made unavailable (varied off) without restarting the system. An independent disk pool can be either a) privately connected to a single system b) switchable among multiple systems in a clustering environment or c) duplicated at another site by geographic mirroring. Synonymous with independent auxiliary storage pool (ASP).
- insync
- In geographic mirroring, pertaining to the mirror copy data state that indicates that the production and mirror copy have exactly the same contents.
- library namespace
- An attribute that can be set for the current thread. The library namespace is the set of objects and libraries that can be accessed in any independent disk pools in a disk pool group plus the libraries in the system disk pool and basic user disk pools (ASPs 2-32) using the regular library-qualified object name syntax. The Set Auxiliary Storage Pool Group (SETASPGRP) command sets the auxiliary storage pool (ASP) group for the current thread.
- mirror copy
- In geographic mirroring, an independent disk pool that is being geographically mirrored so that it is a replica of the production copy of the independent disk pool. If a switchover or failover causes the system that owns the mirror copy to become the current primary node, the mirror copy becomes the production copy of the independent disk pool. The mirror copy has current data only when geographic mirroring is active.
- mirror copy state
- In geographic mirroring, the geographic mirroring state of the mirror copy; for example, active, resume pending, resuming, and suspended.
- mirror copy data state
- In geographic mirroring, the current status of the data that is being geographically mirrored; for example, insync, usable, and unusable.
- primary disk pool
- An independent disk pool that defines a collection of directories and libraries and may have other secondary disk pools associated with it. A primary disk pool also defines a database for itself and other disk pools that may be added in its disk pool group. Primary disk pools can only be implemented on V5R2 or later of OS/400®.
- production copy
- In geographic mirroring, the independent disk pool to which all production operations are directed. All disk write operations are directed here first and are then replicated to the mirror copy of the independent disk pool. The production copy always has current data.
- reattach
- In geographic mirroring, to reassociate the detached mirror copy with its production copy after user operations on the detached mirror copy are completed. When the detached mirror copy is reattached, it is automatically synchronized to match the production copy again. All data on the detached mirror copy is cleared before it is reattached to the production copy.
- resume
- In geographic mirroring, to start performing geographic mirroring again after it is suspended.
- resume pending state
- In geographic mirroring, pertaining to the configuration state of a mirror copy that indicates that geographic mirroring requires synchronization but that the disk pool is currently unavailable. When the disk pool is made available, the mirror copy will be synchronized with the current data from the production copy.
- resuming state
- In geographic mirroring, the configuration state of the mirror copy that attempts to perform geographic mirroring and synchronization when the independent disk pool is available. The mirror copy state is resuming when it is not suspended or active.
- secondary disk pool
- An independent disk pool that defines a collection of directories and libraries and must be associated with a primary disk pool. Secondary disk pools can only be implemented on V5R2 or later of OS/400. See
- site
- In cross-site mirroring, a location containing a node or nodes with access to either the production copy or mirror copy. The sites can be in close proximity or geographically dispersed.
- site primary node
- In cross-site mirroring, a node that owns the independent disk pool, either the production copy or mirror copy, at a particular site. The production-site primary node is also the primary node for the cluster resource group. The mirror-site primary node is a backup node in a cluster resource group.
- source system
- The system that currently owns the production copy of an independent disk pool in a cross-site mirroring (XSM) environment. The target system is a backup node in the cluster resource group and is the mirror site primary node. Changes to the production copy of an independent disk pool are replicated to the mirror copy of the independent disk pool that exist on a backup node within the recovery domain.
- suspend
- In geographic mirroring, to temporarily stop performing geographic mirroring. If the mirror copy contained usable data when suspended, the mirror copy still contains usable, though possibly outdated, data.
- suspended state
- In geographic mirroring, pertaining to the configuration state of the mirror copy that does not attempt to perform geographic mirroring when the independent disk pool is available. The mirror copy state is suspended when it is not resuming or active.
- switchable entity
- The physical resource containing the independent disk pools that can be switched between systems in a cluster. This can be a expansion unit containing disk units in a multiple system environment. This might also be an IOP containing disk units in an LPAR environment.
- switchover
- A cluster event where the primary database server or application server switches over to a backup system due to the manual intervention from the cluster management interface.
full synchronization
- The geographic mirroring processing that copies data from the production
copy to the mirror copy. During synchronization the mirror copy contains
unusable data. When synchronization is completed, the mirror copy contains
usable data.
- partial synchronization
- While the system is in a suspended state, changes made to the production
copy are not sent to the mirror copy. If the production copy is suspended
with tracking, any changes made to the production copy are instead tracked.
Once geographic mirror is resumed and partial synchronization is started,
those tracked changes are then sent to the mirror copy.
- synchronous
- In geographic mirroring, pertaining to the mode of geographic mirroring where the program that issues the update waits until the operation is completed to disk on both the production copy and the mirror copy. This mode ensures that once control is returned to the client, the operation is accurately reflected on both the production copy and the mirror copy.
- SYSBAS
- In the character-based interface, refers to the system disk pool 1 and all configured basic disk pools 2 through 32. Independent disk pools 33 through 255 are not included.
- target system
- A system that currently owns a mirror copy of an independent ASP in a cross-site mirroring (XSM) environment. Changes to the production copy of an independent disk pool on the source system are replicated to the mirror copy of the independent disk pool that exists on a target system.
- tracking
- A process that remembers changes that occur while geographic mirroring
is suspended. When geographic mirroring resumes the system only synchronizes
the tracked changes and does not perform a full synchronization.
- UDFS disk pool
- An independent disk pool that contains only user-defined file systems. It cannot be a member of a disk pool group unless it is converted to a primary or secondary disk pool.
- unusable
- In geographic mirroring, pertaining to the mirror copy data state that
indicates that the mirror copy contains incoherent data. This occurs:
- During synchronization because synchronization does not preserve the order of writes.
- When the system performs geographic mirroring in asynchronous mode.
Note:The mirror copy becomes usable during a vary-off of
the production copy of the independent disk pool. - usable
- In geographic mirroring, pertaining to the mirror copy data state that
indicates that the correct order of updates to the mirror copy from the production
copy is being preserved, but the mirror copy may be outdated. The usable mirror
copy data state occurs:
- When the system performs geographic mirroring in synchronous mode.
- After successfully suspending geographic mirroring.
- When mirror copy is successfully detached.
Note:- The mirror copy becomes usable during a vary-off of the production copy of the independent disk pool.
- Number 1 and 2 do not apply during a synchronization.
- vary off
- To make an independent disk pool unavailable for its normal, intended use. All of the primary and secondary disk pools in a disk pool group will vary off together. Synonymous with make unavailable.
- vary on
- To make an independent disk pool available for its normal, intended use. All of the primary and secondary disk pools in a disk pool group are varied on together. Synonymous with make available.