Database Reference
In-Depth Information
Oracle Clusterware 12c Technology Stack
Cluster Ready Service
Technology Stack
High Availability Service
Technology Stack
CRS
CSS
appagent
GPNPD
ologgerd
cssdagent
ASM
GIPC
CTSS
EVM
mDNS
scriptagent
mDNS
oraagent
ONS
oraagent
osymond
orarootagent
orarootagent
Figure 2-2.
Oracle Clusterware 12cR1 stack
High Availability Cluster Service Stack
The High Availability Cluster Service stack is the lower stack of the Oracle Clusterware. It is based on the Oracle High
Availability Service (
OHAS
) daemon. The OAHS is responsible for starting all other clusterware processes. In the next
section, we will discuss the details of the clusterware sequences.
OHAS uses and maintains the information in OLR. The High Availability Cluster Service stack consists of the
following daemons and services:
GPnP daemon (
GPnPD
): This daemon accesses and maintains the GPnP profile and ensures that all the nodes
have the current profile. When OCR is stored in an ASM diskgroup, during the initial startup of the clusterware, OCR is
not available as the ASM is not available; the GPnP profile contains enough information to start the Clusterware.
Oracle Grid Naming Service (
GNS
): This process provides the name resolutions with the cluster. With 12cR1, GNS
can be used for multiple clusters in contrast to the single-cluster version.
Grid Interprocess Communication (
GIPC
): This daemon supports Grid Infrastructure communication by
enabling Redundant Interconnect Usage.
Multicast Domain Name Service (
mDNS
): This daemon works with GNS to perform name resolution.
This stack also includes the System Monitor Service daemon (
osysmond
) and Cluster Logger Service daemon
(
ologgerd
).
The CRS Stack
The CRS stack is an upper-level stack of the Oracle Clusterware which requires the support of the services of the lower
High Availability Cluster Service stack. The CRS stack includes the following daemons and services:
CRS: This service is primarily responsible for managing high availability operations. The CRS daemon (CRSD)
manages the cluster resource's start, stop monitor, and failover operations. CRS maintains the configuration
information in OCR. If the cluster has an Oracle RAC database, the resources managed by CRS include the Oracle
database and its instances, listener, ASM instance, VIPs, and so on. This service runs as the
crs.bin
process on
Linux/Unix and
OracleOHService
on Windows.
CSS: This service manages and monitors the node membership in the cluster and updates the node status information
in VD. This service runs as the
ocssd.bin
process on Linux/Unix and
OracleOHService (ocssd.exe)
on Windows.
CSS Agent: This process monitors, starts, and stops the CSS. This service runs as the
cssdagent
process on
Linux/Unix and
cssdagent.exe
on Windows.
CSS Monitor: This process works with the
cssdagent
process to provide the I/O fencing to ensure data integrity
by rebooting the RAC node in case there is an issue with the
ocssd.bin
process, a CPU starvation, or an OS locked up.
This service runs as
cssdmonitor
on Linux/Unix or
cssdmonitor.exe
on Windows. Both
cssdagent
and
cssdmonitor
are the new features started in 11gR2 that replace the previous Oracle Process Monitor daemon (
oprocd
) in 11gR1.
