– A dedicated S/390 Parallel Channel adapter is required.It cannot be
shared with any other OS/2 applications.
– A maximum of 16 active channel programs per card is supported.
– Multi-path is not supported (two channels to the same device controller).
Datamovement
Minimizing the number of channel control words (CCWs) required to move data
is key to maximizing performance for a channel-attached device.The larger
the amount of data per CCW, the better the performance.
Printing in page mode is equivalent to using a larger block size on tapes.The
number of CCWs per page is less, and the number of data bytes per CCW is
greater, so in general, the system can print faster on page printers in page
mode than on printers in line mode.
Number of devices supported
The IBM S/390 Integrated Server supports up to four S/390 Parallel Channel
adapter cards.One S/390 Parallel Channel adapter can support 1-255
devices. However, there cannot be more than 16 active channel programs at
the same time per card.
Note: The IBM S/390 Integrated Server has a system limit of 255 total devices
both emulated and channel attached.
Byte mode or block mode
One S/390 Parallel Channel adapter can support both S/370 and S/390 printers
and tape drives.Unlike S/390 channels, you can intermix modes and speeds
(byte, block or data streaming at DCI, 3 or 4.5 mb/s) for different devices
attached to same S/390 Parallel Channel adapter simultaneously.
Alternatives
If the expected data movement or number of I/O operations exceeds the
preceding guidelines, consider using PC devices rather than S/390 channel
attached devices.Here are two examples:
– Use a PC laser printer connected to a parallel printer port or to a LAN to
reduce the workload on a channel attached impact line printer.
– Replace coax-attached terminals (on a 3174) with workstations on a LAN,
or replace the channel-attached 3174 with a Token Ring attached 3174.
S/390 ESCON Channel Adapter
Generalstatement
The S/390 ESCON Channel Adapter provides channel-attach capability of all
ESCON Channel attached devices to the IBM S/390 Integrated Server.The
IBM S/390 Integrated Server supports a maximum of two Serial Channel
adapters in any combination.
The primary purpose for attaching ESCON devices to the S/390 Integrated
Server is for connectivity. The performance of integrated I/O devices will
probably be better, in most cases, than ESCON-attached devices.Because of
the PCI bus structure in the IOSP, S/390 Integrated Server ESCON
performance will not match that of traditional mainframe ESCON channels.
Some typical attachments are:
22 S/390  Integrated Server