Developers Guide

Technology overview
8 Dell EMC SC Series Storage with Oracle ASM | CML1111
Node 1 Node 2 Node 4Node 3
DB1 DB1 DB1 DB2DB2
ASM ASMASM
Fabric
Oracle
interconnect
ASM nodes
(DB and ASM instance)
ASM
DATA FRA
Traditional ASM configuration with dedicated ASM instance for each database server
For LUNs intended for ASM, there are several tools at the OS level that can be used to manage them and
provide consistent device naming and permission persistency: ASMLib, ASM Filter Driver (ASMFD), or
UDEV. This document briefly reviews ASMLib. For additional information on ASMLib, ASMFD, UDEV, and the
configuration and benefits of using ASM, see the document, Dell EMC SC Series Arrays and Oracle.
2.3.1 Oracle Flex ASM features
Prior to the availability of Flex ASM, an ASM instance is required on each database server where there is a
database instance. This creates the possibility of a single point of failure with the ASM architecture on any
one of the database servers. If an ASM instance fails, so would the corresponding database instance.
Since ASM manages the physical access to ASM files and its metadata, a shutdown of the ASM instance will
cause the client database instances to shut down as well. Flex ASM mitigates this issue by starting another
ASM instance in the cluster and reroutes ASM traffic to an available ASM instance in the cluster. The selected
ASM instance is the one with the least amount of activity. Rerouting ASM traffic resolves the single point of
failure in the event that an ASM instance fails, and provides a highly scalable, massively parallel, and highly
available framework. ASM traffic can reside on either the private Oracle RAC interconnect, or an optional
dedicated network for ASM traffic. The number of nodes running an ASM instance in a Flex ASM
configuration is three by default, but is controlled by the ASM cardinality and can be altered.