GraalVM is a separate product developed by an unrelated team. Its enterprise flavour is not considered an enterprise flavour of the JDK. The closest to an enterprise JDK from Oracle I can think of is the "Enterprise Performance Pack" for the 12-year-old Java 8, but it has nothing that isn't in the free and open recent releases (which actually include many more performance enhancements).
The idea there is that it's cheaper for companies with legacy software that isn't actively maintained to pay for some portion of the performance improvements in modern JVM generations than to ramp up maintenance to upgrade to modern Java, and this can help fund the continued evolution of OpenJDK.
what happens when the legacy code is migrated to the new java, which is supposedly easier to upgrade post java 8? who will pay for long term support if upgrading is so easy?
There's always legacy systems; it's part of the natural lifecycle of software. Also, what you buy is any kind of support, regardless of the version you're on. Support doesn't mean access to patches but an SLA for the tickets you file.
You’re the only one who put “Open” in there. Both your parent and grandparent said JDK.
GraalVM is a separate product developed by an unrelated team. Its enterprise flavour is not considered an enterprise flavour of the JDK. The closest to an enterprise JDK from Oracle I can think of is the "Enterprise Performance Pack" for the 12-year-old Java 8, but it has nothing that isn't in the free and open recent releases (which actually include many more performance enhancements).
The idea there is that it's cheaper for companies with legacy software that isn't actively maintained to pay for some portion of the performance improvements in modern JVM generations than to ramp up maintenance to upgrade to modern Java, and this can help fund the continued evolution of OpenJDK.
what happens when the legacy code is migrated to the new java, which is supposedly easier to upgrade post java 8? who will pay for long term support if upgrading is so easy?
There's always legacy systems; it's part of the natural lifecycle of software. Also, what you buy is any kind of support, regardless of the version you're on. Support doesn't mean access to patches but an SLA for the tickets you file.
Because people keep forgetting Java is like C and C++, there are plenty of JDKs to chose from, and not all of them are related to the same codebase.