Veritas Storage Foundation™ 5.0.1 for Oracle RAC Installation, Configuration, and Administrator's Guide Extracts for the HP Serviceguard Storage Management Suite on HP-UX 11i v3

Table 1-1 SG SMS Serviceguard Cluster File System for RAC Bundle Component Products (continued)
DescriptionComponent Product
Manages Oracle RAC databases and infrastructure components.Serviceguard
Manage cluster membership and communications between cluster nodes.RAC Extensions (Serviceguard
eRAC)
Communication Infrastructure
To understand the communication infrastructure, review the data flow and communication
requirements.
Data Flow
The CVM, CFS, ODM, and Oracle Real Application Clusters (RAC) elements reflect the overall
data flow, or data stack, from an instance running on a server to the shared storage. The various
Oracle processes composing an instance—such as DB Writers, Log Writer, Checkpoint, Archiver,
and Server—read and write data to the storage through the I/O stack in the diagram. Oracle
communicates through the ODM interface to CFS, which in turn accesses the storage through
the CVM.
Figure 1-2 Data Stack
Oracle
RAC
Instance
Oracle
RAC
Instance
LGWR
ARCH
CKPT
DBWR
ODM ODM
CFSCFS
CVM CVM
Redo
Log
Files
Archive
Storage
Data
and
Control
Files
Disk I/O Disk I/O
LGWR
ARCH
CKPT
DBWR
Communication Requirements
End-users on a client system are unaware that they are accessing a database hosted by multiple
instances. The key to performing I/O to a database accessed by multiple instances is
communication between the processes. Each layer or component in the data stack must reliably
communicate with its peer on other nodes to function properly. RAC instances must communicate
to coordinate protection of data blocks in the database. ODM processes must communicate to
coordinate data file protection and access across the cluster. CFS coordinates metadata updates
for file systems, while CVM coordinates the status of logical volumes and maps.
14 Introducing Serviceguard Extension for RAC