(Originally posted 2007-10-17.)
Following on from Coupling Facility Async / Sync Thresholds – They Are A’Changin’ I’ve been informed by Development there is a new improved write up on how the Dynamic Sync/Async conversion works in Chapter 6 of the z/OS Release 9: Setting Up A Sysplex manual. I’ve read it and it is VERY good.
One thing to pull out is that there isn’t just one threshold… There are different thresholds for Lock vs List and Cache structures, for Duplex versus Simplex (aka Non-Duplex), and by machine. The thresholds that have increased are not the ones for the Duplex case. Those stayed the same. (The thing that got me sight of the new documentation was asking what effect Duplexing had on the thresholds, by the way.)
Not coincidentally I was in a customer yesterday planning how we are going to measure a test with DB2 Data Sharing at a distance of over 20km. Part of that will be experimenting with turning off System-Managed Duplexing but not (we think) User-Managed Duplexing (aka GBP Duplexing). Without in any way betraying confidences I’ll see if I can write up the lessons we’ll have learned over the coming weeks and months.
So do take a look at the new description. It is really very good.