Mainframe, MVS and zOS Discussion

Hi,

How does the upgrade in mainframe happen? And how is it that mainframe computers can run uninterrupted during software upgrades and "hardware hot swaps"?

The first thing to clarify is, are you talking about hardware or software when you say "upgrade in mainframe"?

For hardware upgrades, a few components are hot-swappable but in general most upgrades require the CEC (the hardware box) to be down. Other CEC in the sysplex may remain up, so only those subsystems running on the affected hardware would be down.

For software upgrades, a further distinction is made between system upgrades and ISV (independent software vendor) upgrades. IBM has a product specifically designed to upgrade system software (it is called SMP/E), and this product is used to do the upgrade. Depending upon what is being upgraded, an upgrade may not require more than the specific subsystem being upgraded to be brought down and back up -- but if certain system libraries are being changed (LPA or linklist for example) then an IPL is required to complete the upgrade. SMP/E provides HOLD data about what is required to complete the upgrade (IPL, LLA refresh, or whatever). Some ISV software uses SMP/E and installs the same as system software; other ISV software uses a different upgrade mechanism (there are too many to describe).

I wanted to understand the software upgrade.

Can we practice the SMP/E on Hercules or some other set-up at home?

Thanks for your answers so far.