IBM eServer zSeries 900 Technical Guide

Chapter 5. Sysplex functions 187

򐂰 Be prepared to provide additional z/OS CPU capacity when the workload’s CF operations

become duplexed. Provide sufficient coupling facility CP resources so that coupling facility

CP utilization remains below 50% in all CF images.

򐂰 Provide “balanced” coupling facility CP capacity between duplexed pairs of CFs. Avoid

significant imbalances such as one CF with shared CPs and the other CF with dedicated

CPs, CFs with wildly disparate numbers of CPs, CFs of different machine types with very

different raw processor speed, and so forth.

򐂰 As z/OS-to-CF and CF-to-CF distances increase, monitor the coupling facility link

subchannel and path-busy status. If more than 10% of all messages are being delayed on

the CF link due to subchannel or path busy conditions, either migrate to peer mode links to

increase the number of subchannels for each link, or configure an additional link.

򐂰 In a GDPS/PPRC multi-site configuration, do not duplex CF structure data between

coupling facilities located in different sites; rather, if desired, duplex the structures between

two coupling facilities located at the same site. CF structure data is not preserved in GDPS

site failover situations, regardless of duplexing.

System-managed CF duplexing has the following prerequisites:

򐂰 All systems in the Parallel Sysplex must be upgraded to z/OS 1.2 or later.

򐂰 Check the following APARs:

– OW41617 enables the format utility to process the SMDUPLEX keyword needed to

implement the new CFRM CDS version.

– APARs listed in the CFDUPLEX PSP bucket.

– OW45976 supports Sender links on the Coupling Facilities.

򐂰 G5/G6 CF running driver 26 and CFCC level 11.

򐂰 z800/z900 CF running driver 3G and CFCC level 12.

A technical paper on system-managed CF structure duplexing is available at:

http://www-1.ibm.com/servers/eserver/zseries/library/techpapers/gm130103.html

It includes a sample migration plan, describes how to monitor this new Parallel Sysplex

technology and how to determine its cost/benefit in your environment, and gives setup

recommendations.

5.4 Geographically Dispersed Parallel Sysplex

Geographically Dispersed Parallel Sysplex (GDPS) is a multisite application availability

solution that provides the capability to manage the remote copy configuration and storage

subsystem(s), automates Parallel Sysplex operational tasks, and performs failure recovery

from a single point of control, thereby improving application availability. GDPS supports all

transaction managers (for example, CICS TS and IMS) and database managers (such as

DB2, IMS, and VSAM), as well as WebSphere Application Server, and is enabled by means

of the following key IBM technologies and architectures:

򐂰 Parallel Sysplex

򐂰 System Automation for OS/390

򐂰 Enterprise Storage Server (ESS)

򐂰 Peer-to-Peer Virtual Tape Server (PtP VTS)

򐂰 Optical Dense Wavelength Division Multiplexer (DWDM)