Database Reference
In-Depth Information
Figure 2-4. The pre-12c ASM configuration with one ASM instance per cluster node
Flex ASM removes the strict requirement to have one, and only one ASM instance per cluster node. Instead, with
Flex ASM enabled, Oracle will create three ASM instances in the cluster, regardless of cluster size. The number of
ASM instances can of course be configured, most importantly when non 12c databases are supposed to be hosted on
the 12c Grid Infrastructure deployment. In such situations you will need to operate Flex ASM in the same way ASM
operated in the earlier release. Figure 2-5 shows a four-node RAC with Flex ASM enabled. All databases have already
been migrated to 12c.
Figure 2-5. Schematic display of a Flex ASM configuration in a four-node cluster, public and management network are
not shown
Flex ASM can be configured from the start during the installation of Grid Infrastructure and is mandatory if you
are planning on using a Flex Cluster (another new RAC 12c feature). Alternatively an existing configuration can be
changed to Flex ASM using the ASM Configuration Assistant after the ASM spfile, password file, and the OCR and
voting disks are all stored in a disk group within ASM.
ASM traffic can be sent over the private network but might collide with existing workloads. Thankfully there is an
option to allow the ASM traffic to use a dedicated network, as shown in Figure 2-5 . If a dedicated network is used,
 
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