Logical Channel SubSystem (LCSS) Spanning
The concept of spanning channels provides the ability for
a channel to be conﬁ gured to multiple LCSSs and therefore
they may be transparently shared by any/all of the logical
partitions in those LCSSs. Normal Multiple Image Facility
(MIF) sharing of a channel is conﬁ ned to a single LCSS.
The z990 supports the spanning of the channels types: IC,
HiperSockets, FICON Express, OSA-Express. Note: ESCON
architecture helps prevent the spanning of ESCON channels.
IC Channel Spanning
z990 Channels and I/O Connectivity
A z990 with all three I/O cages installed has a total of 84
I/O slots. These slots can be plugged with a mixture of fea-
tures providing the I/O connectivity, networking connectiv-
ity, coupling and cryptographic capability of the server.
Up to 1024 ESCON Channels
The high density ESCON feature has 16 ports, 15 of which
can be activated for customer use. One port is always
reserved as a spare which is activated in the event of a
failure of one of the other ports. For high availability the ini-
tial order of ESCON features will deliver two cards and the
active ports will be distributed across those cards. After
the initial install the ESCON features are installed in incre-
ments of one. ESCON channels are available in four-port
increments and are activated using IBM Licensed Internal
Code, Conﬁ guration Control (LIC CC).
Up to 120 FICON Express Channels
The z990 supports up to 120 FICON Express channels.
FICON Express is available in long wavelength (LX) and
short wavelength (SX) features. Each FICON Express fea-
ture has two independent ports which support two chan-
nels per card. The LX and SX cannot be intermixed on a
single feature. The maximum number of FICON Express
features is 60 which can be installed across three I/O
cages with a maximum of 20 features per I/O cage.
The z990 supports up to 120 FCP channels for attach-
ment to Small Computer System Interface (SCSI) disks in
a Linux environment. The same two-port FICON Express
feature card used for FICON Express channels can also
be used for Fibre Channel Protocol (FCP) channels. FCP