System Memory Size
There are two types of system memory, S/390 memory and the I/O and Service
Processor (IOSP) memory.
1. The P/390 has 256MB of ECC memory for use by the S/390 operating system
and S/390 applications. This should be sufficient for any VM/ESA, VSE/ESA,
and most OS/390 systems.Memory-intensive systems should consider using
I/O and Service Processor (IOSP) memory (also referred to as PC memory) to
emulate S/390 Expanded Storage (described below).
2. The P/390 code includes the emulation of S/390 Expanded Storage by using
the I/O and Service Processor (IOSP) memory.The I/O and Service Processor
(IOSP) memory consists of 128MB. This 128MB is standard and is the only
Note: Ensure that OS/2 always has sufficient memory for itself.For
with small cache or expanded storage sizes (less than 16MB), 48MB for
OS/2 should be sufficient.
S/370 or S/390 Tape Drives
If you exchange S/390 tapes with other S/370 and/or S/390, you need to
ensure the tape media that you choose is usable by those machines.Standard
IBM 3420, 3480, or 3490 tape drives can be channel attached via the S/390
Parallel Channel adapter or S/390 ESCON adapter.There is also a 3490E
tape drive that may be SCSI-attached using a differential SCSI adapter.
Tape size and compression
Figure 4 shows tape sizes with and without compression.
– The P/390 I/O subsystem does not support the READ BACKWARDS CCW
unless the SKIP bit is on.This may affect certain tape utility programs.It
applies to all tapes, whether emulated or SCSI-attached.
– The only supported SCSI-attached 3490 tape drive is the IBM 3490-F01.
(The use of the Adaptec AHA2944UW differential SCSI controller is
required for these drives.)
– The 4mm DAT tape drive is only provided for loading software and service.
It is not recommended to be used for backup procedures.
Figure 4. TapeSizewithandwithoutCompression
Tape Size Without
3420 120MB N/A
3422 120MB N/A
3480 200MB 400MB
3490E N/A 2.3GB
Chapter 7.Planning Guide25