Database Reference
In-Depth Information
Level 3:
The
CRSD
spawns two
CRSD
agents:
CRSD orarootagent
and
CRSD oracleagent
.
Level 4:
On this level, the
CRSD orarootagent
is responsible for starting the following resources:
Network resource: for the public network
•
•
SCAN VIPs
•
Node VIPs: VIPs for each node
•
ACFS Registry
•
GNS VIP: VIP for GNS if you use the GNS option
Then, the
CRSD orarootagent
is responsible for starting the rest of the resources as follows:
ASM Resource: ASM Instance(s) resource
•
•
Diskgroup: Used for managing/monitoring ASM diskgroups.
•
DB Resource: Used for monitoring and managing the DB and instances
•
SCAN listener: Listener for SCAN listening on SCAN VIP
•
SCAN VIP: Single Client Access Name VIP
•
Listener: Node listener listening on the Node VIP
•
Services: Database services
•
ONS
•
eONS: Enhanced ONS
•
GSD: For 9i backward compatibility
•
GNS (optional): performs name resolution
ASM and Clusterware: Which One is Started First?
If you have used Oracle RAC 10g and 11gR1, you might remember that the Oracle Clusterware stack has to be up
before the ASM instance starts on the node. Because 11gR2, OCR, and VD also can be stored in ASM, the million-
dollar question in everyone's mind is, “Which one is started first?” This section will answer that interesting question.
The Clusterware startup sequence that we just discussed gives the solution: ASM is a part of the CRS of the
Clusterware and it is started at Level 3 after the high availability stack is started and before
CRSD
is started. Then,
the question is, “How does the Clusterware get the stored cluster configuration and the clusterware membership
information, which are normally stored in OCR and VD, respectively, without starting an ASM instance?” The answer
is that during the startup of the high availability stack, the Oracle Clusterware gets the clusterware configuration from
OLR and the
GPnP
profile instead of from OCR. Because these two components are stored in the $GRID_HOME in the
local disk, the ASM instance and ASM diskgroup are not needed for the startup of the high availability stack. Oracle
Clusterware also doesn't rely on an ASM instance to access the VD. The location of the VD file is in the ASM disk
header. We can see the location information with the following command:
$ kfed read /dev/dm-8 | grep -E 'vfstart|vfend'
kfdhdb.vfstart: 352 ; 0x0ec: 0x00000160
kfdhdb.vfend: 384 ; 0x0f0: 0x00000180
The
kfdhdb.vfstart
is the begin AU offset of the VD file, and the
kfdhdb.vfend
indicates the end AU offset of the
VD file. Oracle Clusterware uses the values of
kfdhdb.vfstart
and
kfdhdb.vfend
to locate the VD file
.
