Google Cloud announces Dual Run to ease mainframe migration to cloud

Not much detail but Santander post has more details https://www.santander.com/en/press-room/press-releases/2022/...

> To enable the transformation and modernization of its core banking, the bank is using Gravity, a bespoke internal software which has been developed in-house and allows parallel processing, meaning the bank can simultaneously run workloads on its existing mainframe and on the cloud, allowing it to perform real-time testing with no disruption to its businesses.

My guess is that this software captures CICS transactions, sends them to "the cloud", and then validates if both system provide the same results. I have no idea how they synchronize BATCHs input/outputs but given the goal to drop "mainframe" they probably already migrated the database to a cloud hosted one so when a BATCH is updating data is already updating CLOUD data.

I think the key thing in this article is talking about compliance.

“Customers can test that [the cloud workload] is performing as expected, that the dependencies check out and that they can meet their compliance/auditor needs before transitioning completely to the cloud environment,” Gupta said at the press event.

The reason banks don't move away from mainframes is that they can't get identical results from other technologies in a way that can be certified by an independent auditor.

> Why is this important? Well for starters, 44 of the top 50 banks and 23 of the top 25 largest U.S. retailers still use mainframes, according to Google.

I'd rather be interested which 6 top US banks already manage to run without mainframes. And if they can run their systems cheaper/more flexibly or are stuck with SAP/Oracle contracts that are as expensive and hard to change.

Given how protective Big Blue is of its mainframes. Has the Black Gate of Armonk swung open and the Nazgul on their way to Mountain View? /s

Cool, but can I connect to it using a 3274 controller and an attached 3278 terminal?