Database Reference
In-Depth Information
3.
Run the start_udev command to apply the newly created rules:
[root@k2r720n1 rules.d]# start_udev
Starting udev: [ OK ]
4.
Check the new ownership and permission settings:
# ls -l /dev/dm-*
brw-rw---- 1 grid asmadmin 253, 8 Oct 29 12:08 /dev/dm-8
brw-rw---- 1 grid asmadmin 253, 9 Oct 29 12:08 /dev/dm-9
In summary, the provisioning of storage volumes for an Oracle RAC Database consists of these steps:
•
Establish redundant paths from RAC hosts to the storage.
•
Design and configure the proper storage volumes and assign these volumes to the RAC hosts
so that these volumes are presented as the block devices on the RAC hosts.
•
Configure multipathing on the block devices by mapping them to the multipath block
device names.
•
Set the proper ownerships and the access permissions on these multipath block device names.
ASM
In the previous section, I discussed storage design and how to present storage volumes as block devices to Oracle RAC
Database hosts. In order to be able to store database files using these block devices, we need to establish database file
systems on these block devices. For the Oracle RAC environment, this file system has to be a cluster file system that
is shared by multiple RAC nodes. Existing volume managers like LVM in Linux and OS file systems like the ext3 file
system in Linux are only for local systems; they are not designed for the cluster environment. Therefore, they cannot
be used for shared storage in the Oracle RAC environment. Prior to Oracle 10g, the Oracle RAC Database was built on
raw devices, which turned out to be very difficult to use and manage due to lack of flexibility. For example it required
one raw device for every file, and the file could not grow or extend. For some Oracle E-Business suite databases which
might need more than 255 files, it actually ran out of the 255 maximum number of available raw devices.
Oracle ASM was initially introduced in Oracle 10g as a volume manager and file system for Oracle data files.
Oracle ASM supports both single-node Oracle Database and Oracle RAC Database. For Oracle RAC Database, Oracle
ASM provides a cluster file system that allows all the RAC nodes to share. With ASM, database files can be created or
grown and expanded as needed. Oracle ASM also provides high availability and performance features such as RAID
configuration and I/O load balancing. Oracle ASM is Oracle's recommended storage solution for Oracle Database.
Oracle ASM has evolved since it was first introduced in Oracle 10gR1. For example, 10gR2 introduced the
command-line interface ASMCMD, multiple database version support, and database storage consolidation with
single instance and RAC. 11gR1 introduced Fast Mirror Resynchronization for ASM redundancy disk groups and ASM
instance rolling upgrade and patching support, separate connect privilege SYSASM. Oracle Grid Infrastructure 11gR2
introduced quite a few new changes in ASM. The most significant ones include combining Oracle Clusterware and
ASM into a single Grid Infrastructure stack, storing Oracle OCR and cluster voting disk files in ASM, and introducing
the ASM cluster file system ACFS and ASM Dynamic Volume Manager ASVM. Oracle 12cR1 also brings many new
features to Oracle ASM and Oracle ACFS. One of the significant new features is Oracle Flex ASM, which decouples the
Oracle ASM instance from the database server and allows database instances to connect the remote ASM instances.
Chapter 4 will give you more details about Oracle Flex ASM. Some other Oracle ASM enhancements introduced in
Oracle 12c include increasing storage limits to support up to 511 storage diskgroups and the maximum Oracle ASM
disk size to 32 Petabytes (PB); ASM shared password file in a disk group; ASM rebalance enhancements and ASM Disk
Resync enhancements; ASMCMD extensions by including icmd command-line interface, a unified shell environment
