SRB And Shutdown

I’ve written several times about System Recovery Boost (SRB) so I’ll try to make this one a quick one.

For reference, previous posts were:

• Really Starting Something
• SRB And SMF
• Third Time’s The Charm For SRB – Or Is it?

From that last one’s title it clearly wasn’t (the end of the matter). It’s worth reading the table with timestamps again.

Notice in particular the first interval – the last one before shutdown – is not boosted. In fact I note that fact in the post.

Some months on I think I now understand why – and I think it’s quite general.

To enable SRB at all you have to enable it in PARMLIB. But it is the default – so you’d have to actively disable it if the z15 (or now z16) support is installed. (One customer has told me they’ve actually done that.)

But enablement isn’t the same as actually invoking it:

• For IPL you don’t have to do anything. You get 60 minutes’ boost automatically.
• For shutdown you have to explicitly start the boost period – using the IEASDBS procedure.

What I think is happening is installations have SRB enabled but don’t invoke IEASDBS to initiate shutdown.

I would evolve shutdown operating procedures to include running IEASDBS. In general, I think SRB (and RPB, for that matter) would benefit from careful planning. So consider running a mini project when installing z15 or z16. If you’re already on z15 note there are enhancements in this area for z16. I also like that SRB / RPB is continuing to evolve. It’s not a “one and done”.

By the way there’s a nice Redpiece on SRB: Introducing IBM Z System Recovery Boost. It’s well worth a read.

In parting, I should confess I haven’t established how CPU intensive shutdown and IPL are, more how parallel. Perhaps that’s something I should investigate in the future. If I draw worthwhile conclusions I might well write about them here.