Veritas Storage Foundation 5.1 SP1 for Oracle RAC Administrator"s Guide (5900-1512, April 2011)

node. For example, before creating a new data file with a specific name, ODM
checks with other nodes to see if the file name is already in use.
Veritas ODM performance enhancements
Veritas ODM enables the following performance benefits provided by Oracle Disk
Manager:
■ Locking for data integrity.
■ Few system calls and context switches.
■ Increased I/O parallelism.
■ Efficient file creation and disk allocation.
Databases using file systems typically incur additional overhead:
■ Extra CPU and memory usage to read data from underlying disks to the file
system cache. This scenario requires copying data from the file system cache
to the Oracle cache.
■ File locking that allows for only a single writer at a time. Allowing Oracle to
perform locking allows for finer granularity of locking at the row level.
■ File systems generally go through a standard Sync I/O library when performing
I/O. Oracle can make use of Kernel Async I/O libraries (KAIO) with raw devices
to improve performance.
ODM communication
ODM uses port d to communicate with ODM instances on other nodes in the
cluster.
Veritas Cluster Server
Veritas Cluster Server (VCS) directs SF Oracle RAC operations by controlling the
startup and shutdown of components layers and providing monitoring and
notification for failures.
In a typical SF Oracle RAC configuration, the Oracle RAC service groups for VCS
run as "parallel" service groups rather than "failover" service groups; in the event
of a failure, VCS does not attempt to migrate a failed service group. Instead, the
software enables you to configure the group to restart on failure.
VCS architecture
The High Availability Daemon (HAD) is the main VCS daemon running on each
node. HAD tracks changes in the cluster configuration and monitors resource
35Overview of Veritas Storage Foundation for Oracle RAC
Component products and processes of SF Oracle RAC