Oracle Database 18c: why Oracle skipped 6 releases?

“If you’re confused as to why Oracle skipped 6 releases, it may be simpler to regard Oracle Database 18c  as  Oracle Database 12c Release 2 12.2.0.2, where Oracle simply changed the naming to reflect the year in which the product is released.

Oracle Database 18c is the first version of the product to follow a yearly release pattern. “

https://blogs.oracle.com/database/oracle-database-18c-:-now-available-on-the-oracle-cloud-and-oracle-engineered-systems

Oracle DB Support Roadmap 2019

What is a Flex ASM and how to check if it is enabled?

In versions prior to 12c, the ASM instance needed to be run on each of the nodes of the cluster. In case ASM was not able to start, the database instance located on the same node was not able to come up also. There were a hard dependency between database and ASM instances.

With Oracle Flex ASM, databases are able to connect remote ASM using network connection(ASM network). In case of ASM instance fails, the database instance will reconnect to another ASM instance on another node. This feature is called Oracle Flex ASM.

Check if you are using such a great feature using the following command:

[grid@rac1 ~]$ asmcmd
ASMCMD> showclustermode
ASM cluster : Flex mode enabled