IBM 990 - Manual (Page 177)

Chapter 7. Sysplex functions 165
Refer to Table 7-4 for an overview of the CF link connectivity options for the various supported
servers.
Table 7-4 z990 CF link connectivity
Peer mode links
There are several advantages in using peer mode links. First of all, peer mode links operate
on a higher bandwidth than the equivalent compatibility mode link. A single CHPID (one side
of the link) can be both sender and receiver; this means that a single CHPID can be shared
between multiple OS logical partitions and one Coupling Link logical partition. The number of
link buffers provided when peer mode links are used is seven per link compared to two per
link in compatibility mode; this is particularly important with System-Managed CF Structure
Duplexing. Peer links have 224 KB data buffer space compared to 8 KB on compatibility
mode links; this is especially important for long distances, as it reduces the handshaking for
large data transfers.
z/OS and/or OS/390 images and Coupling Facility images may be running on the same or on
separate servers. Every z/OS or OS/390 image in a Parallel Sysplex must have at least one
coupling link to each CF image.
Maximum number of links per z990 64 b
a. A maximum of 32 ISC-3s can be defined in compatibility mode, which operates up to 1 Gb/s.
b. The maximum number of external and internal Coupling Links combined (ICB-2, ICB-3,
ICB-4, ISC-3, and active IC links) cannot exceed 64 per system.
Connectivity
options z990 ISC-3 z990 ICB-2 z990 ICB-3 z990 ICB-4
G5/G6 ISC 1 Gbps Compat
Mode N/A N/A N/A
z800/z900 ISC-3 2 Gbps
Peer Mode
a
a. 1 Gbps when 20km RPQ 8P2197 is installed.
N/A N/A N/A
z890/z990 ISC-3 2 Gbps
Peer Mode
a
N/A N/A N/A
G5/G6 ICB N/A 333 MBps
Compat Mode N/A N/A
z900 ICB-2 N/A Not supported N/A N/A
z990 ICB-2 N/A Not supported N/A N/A
z900 ICB-3 N/A N/A 1 GByte/sec
Peer Mode N/A
z990/z890 ICB-3 N/A N/A 1 GByte/sec, Peer
mode,
Recommendation
use ICB-4 N/A
z990/z890 ICB-4 N/A N/A N/A 2 GBps
Peer Mode
Link Type z990 Max