Thomas Kurian, one of Oracle's longest serving executives in charge of Oracle's all-important cloud business, has officially left for an extended leave of absence. Apparently he did so somewhat abruptly and doors may have been slammed. The rumours claim Kurian's good-bye was a resignation, although Oracle says that he has not resigned but is simply "taking some time off. We expect him to return soon".

The spat was over the direction Oracle should take with its bet-the-company cloud computing business, reports Bloomberg. Kurian pushed Ellison to allow more of Oracle's software to run on clouds that compete with Oracle, particularly market leaders Amazon and Microsoft.

Kurian is pushing Oracle to embrace multiple clouds — even the clouds of its bitter enemies — the strategy would make a lot of sense.

It's similar to what Microsoft CEO Satya Nadella has done. He realised that it was far less important to push people to use Windows than to ensure that Microsoft's enormous catalogue of software, particularly Office, could run on any device. So, Microsoft built out its cloud to serve up Office 365 to run on any device; it made sure that its Windows Server software could run on other clouds; and it embraced competitive software, like Linux, on its own cloud.

Ellison though faces a slightly different problem in that Amazon has become a major threat to Oracle.

Amazon is trying to get customers to ditch Oracle's database and use Amazon's database instead. Amazon even built a tool to make it easier to move from an Oracle database to an Amazon one. Microsoft also has its own database and has been a bitter competitor with Oracle for years.

Ellison has been building an Oracle cloud that competes with Amazon (and Microsoft) insisting Oracle's cloud is a faster, better way to run the database.  It is pretty risky – if Oracle's customers don't stay within Oracle's own sphere, Oracle could lose them. Ellison's argument is also weakened by the fact that Oracle's cloud is years behind Amazon's in terms of features. It will take Oracle billions of dollars and several years to catch up, even if it can.