IBM z/OS System-Managed CF Structure Duplexing

Customers who are interested in testing and/or deploy-

ing System-Managed CF Structure Duplexing in their

sysplex should review GM13-0103,

System-Managed CF Structure Duplexing

at ibm.com/server/eserver/zseries/

pso or

ibm.com/server/eserver/zseries/library/techpapers/

gm130103.html to understand the performance and other

considerations of using this feature.

Parallel Sysplex Coupling Connectivity

The Coupling Facilities communicate with z/OS and

OS/390 images in the Parallel Sysplex environment over

specialized high-speed links. For availability purposes, it

is recommended that there be at least two links connect-

ing each z/OS or OS/390 image to each CF in a Parallel

Sysplex cluster. As processor performance increases, it is

important to also use faster links so that link performance

does not become constrained. The performance, avail-

ability and distance requirements of a Parallel Sysplex

environment are the key factors that will identify the appro-

priate connectivity option for a given conﬁ guration.

Parallel Sysplex coupling links on the zSeries have been

enhanced with the introduction of Peer Mode. When con-

necting a zSeries server (z990/z900/z800) to a z800 Model

0CF, a z900 Model 100 or a zSeries ICF, the links can be

conﬁ gured to operate in Peer Mode. This allows for higher

data transfer rates to and from the Coupling Facilities. In

Peer Mode, the ﬁ ber-optic single mode coupling link (ISC-

3) provides 200 Gbps capacity, up to 10 km, 100 Gbps

up to 20 km, the ICB-3 link with 1 GBps peak capacity, the

ICB-4 for z990 to z990 connection at 2.0 GBps, and the

IC-3 link with 1.25 GBps capacity. Additional Peer Mode

beneﬁ ts are obtained by enabling the link to be MIFed

between z/OS (or OS/390) and CF LPARs. The peer link

acts simultaneously as both a CF Sender and CF Receiver

link, reducing the number of links required. Larger and

more data buffers and improved protocols also improve

long distance performance. For connectivity to 9672s,

zSeries ISC-3 CF links can be conﬁ gured to run in Com-

patibility Mode with the same characteristics as links on

the 9672 of 100 Gbps. The z900 and z990 also support

ICB-2 links for connectivity to 9672s. The ICB coupling link

speeds described above are theoretical maximums.

GDPS/PPRC Cross Site Parallel Sysplex distance Extended to

100 km

When using a Dense Wave Division Multiplexor (DWDM),

it will be possible via an RPQ to conﬁ gure GDPS/PPRC or

a multi-site Parallel Sysplex with up to 100 km between

the two sites. The immediate advantage of this extended

distance is to potentially decrease the risk that the same

disaster will effect both sites, thus providing the ability

for customers to recover their production applications at

another site. Support for the External Timer Reference

(ETR) links and the Inter System Channel (ISC-3) links

has been increased from the current capability of 50 km

to an extended capability of up to 100 km. The extended

distance support for ETR and ISC-3 links is now consis-

tent with other cross site technologies that already sup-

port 100 km, such as FICON, Peer-to-Peer Remote Copy

(PPRC), and Peer-to-Peer Virtual Tape Server (PtP VTS).

It should be noted that the maximum distance between a

pair of 9037 Sysplex Timers in an Expanded Availability

conﬁ guration remains at 40 km. Therefore, to achieve the

extended distance of 100 km between the two sites, one of