IBM s/390 manual Display PSW and registers, RAS discussion

In most cases, these fields are set by the FLEX-ES license key and you cannot change them. There is an option to make these fields changeable; this option must be specified when the system is ordered. If this option is used, the machine type cannot be set to 1245, 1246, or

1247. Two CLI instructions are associated with this area:

flexes>	display cpuid
flexes>	set cpuid	(only if permitted by the license key)

5.17 Display PSW and registers

You may sometimes need to display the S/390 PSW. You can do this from the flexes prompt provided by the CLI program:

flexes>	d	psw	(displays	psw and	next instruction, if possible)
flexes>	d	g	(displays	general	purpose registers)

5.18 RAS discussion

Is a ThinkPad/EFS system as reliable as a “real” S/390? No. A reliability discussion can quickly become extended and open ended. We need to include Netfinity/EFS systems as part of the following discussion. We can summarize our views this way:

￿A Netfinity/EFS or a ThinkPad/EFS system is not a S/390 (or a z900) system in terms of reliability. It does not have dual instruction units in each processor, or an Application Preservation function, for example.

￿A Netfinity/EFS system is based on a very high-quality Server and is expected to exhibit much better reliability than a typical desktop PC. Contributing factors are:

–ECC memory

This is extremely important in preventing the random lockups and crashes that many PCs experience.

–Use of a RAID adapter

–ECC memory in the RAID adapter, for the same reasons

–Battery operated cache in the RAID adapter

–Multiple, redundant power supplies

–Selection of a very stable Server operating system (UnixWare)

–Absence of random applications (of uncertain trustworthiness) on the Server (That is, games are not downloaded from random sources on the Web, we hope.)

–Thorough physical inspection of the Netfinity hardware by the business partner involved

While this sounds trivial, it contributes to stability.

–Using a UPS system “in front” of the Server

–Better cooling

This is a significant factor for a system that is intended to run continuously.

￿A ThinkPad/EFS is based on a quality laptop system, but this does not compete with a Netfinity/EFS server in many RAS characteristics.

–The ThinkPad does not have RAID protection for its disk(s). With a single disk drive, or, at the most, two drives, there is no practical method to add RAID protection.

–Multiple power supplies are not available.

–ECC memory is not used, for a number of reasons.

Chapter 5. Additional Topics 57