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Data sharing
You can use the ESS to share data among multiple UNIX-based homogeneous host
systems and host systems with Windows NT and Windows 2000. Use the correct
application code or database manager to regulate concurrent read or write access.
For example:
v You could assign an 8-GB disk partition (logical volume) to multiple separate
v Two IBM RS/6000 host systems with the Oracle Parallel Edition could also share
Application software or database manager software is responsible for the integrity of
the database. This includes access management and access locking. The ESS
provides the physical access to the data. Sharing of data is now possible without
transferring files, creating second copies of data, or other methods that you may
have used previously.
IBM Subsystem Device Driver
You can install the IBM Subsystem Device Driver in your open host system to
improve data availability and performance. The IBM Subsystem Device Driver uses
redundant connections between the host server and disk storage in an ESS. These
connections comprise many different components through which data flows during
input and output processes.
Redundancy and the ability to switch between these components provides many
different paths on which the data travels. See IBM Subsystem Device Driver,
Version 1 Release 1 for more information.
System/390 availability features
This section describes the following availability features and other System/390
functions:
v Extended remote copy
v Using Extended Remote Copy for outages
v Concurrent Copy
v Multiple allegiance
v Parallel Access Volumes
For more detailed descriptions of extended remote copy and concurrent copy and
procedures about how to use them, see IBM Advanced Copy Services .
Extended Remote Copy
The ESS supports the Extended Remote Copy (XRC) feature on System/390 hosts.
XRC mirrors data on the ESS to a remote location for disaster recovery. It ensures
data consistency across all volumes that you have defined for mirroring. The
volumes can reside on several different ESSs. XRC can mirror the volumes over
several thousand kilometers from the primary site to the recovery site.
Using Extended Remote Copy for outages
With ESS XRC you can suspend or resume service during an outage. You do not
have to terminate your current data-copy session. You can suspend it and restart it.
UNIX-based host systems.
If host systems are using software that can regulate access to data, then one
host system could write data while a second host system initiates a query.
a single copy of data.
Oracle also runs with other UNIX operating systems.
19
Chapter 1. Introduction
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