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Oracle Clusterware (RAC) Startup Procedure and Use of GPNP Profile and OLR
In todays post I want through some light upon Oracle Clusterware startup procedure. Which process in what sequence etc etc.
So till 10g it was not too difficult but starting from 11g you have possibility to store the voting disk and OCR in ASM which make it a bit difficult but no worry you will get hold of it after this post.
Now from 11g onwards you store Voting disk and OCR in ASM since Voting disk and OCR are the primary component required to start the Clusterware which further starts the Clusterware resources like ASM, Listener, Database etc.
Did you notice something?? What
Which further starts the Clusterware resources like ASM, what but you just told that Voting disk and OCR can be stored in ASM and Clusterware starts the ASM and Clusterware startup itself requires the access of Voting disk and OCR so what starts first ASM or Clusterware what the hell is going on .....I am confused......
Hold On......
That's why you need to read this post.
Lets understand some basic terminologies to get hold on it
What is GPNP Profile?
The GPnP profile is a XML file located at CRS_HOME/profiles/peer as profile.xml. Each node of the cluster maintains a copy of this profile locally and is maintained by ora.gpnpd (GPnP daemon) together with ora.mdnsd (mdns daemon.)
This GPNP profile (profile.xml) contains information like.
Network interfaces for public and private interconnect
ASM server parameter file,
CSS voting disks.
Clustername
Clusterid
Copy the gpnp profile to /tmp location and view it for complete content what it contains.
What is OLR?
In Oracle Clusterware 11g Release 2 an additional component related to the OCR called the Oracle Local Registry (OLR) is installed on each node in the cluster.
The OLR is a local registry for node specific resources. Location of OLR is CRS_HOME/cdata/.olr and Location of olr is stored in /etc/oracle/olr.loc
Some important information which OLR contains
Active crs version
ORA_CRS_HOME
GPnP details
OCR latest backup time and location etc.
This is the first file red to obtain the information to start the CRS stack.
By know you know Oracle GPnP and OLR lets have a look how oracle uses these files and the information stored in this file to initialize and startup the Clusterware
Initialization and Startup of Clusterware
From 11g Release 2 you can store the OCR and Voting disk in ASM, but Clusterware needs OCR and Voting disk to start crsd and cssd and both these files are if in ASM which itself is a resource for the node. So how does the Clusterware starts, which files it accesses to get the information needed to start Clusterware, to resolve this deadlock ( pahle tum pahle tum...) of CRS and ASM Startup, Oracle came up with two local operating system files OLR & GPnP.
When a node of an Oracle Clusterware cluster restarts, OHASD is started by platform-specific means eg /etc/inittab.
OHASD has access to OLR (oracle local registry). OHASD then reads the OLR content and initialize accordingly.
OHASD brings up GPnP (ora.gpnpd)Daemon and CSS (ora.cssd) Daemon.
CSS Daemon has access to the GPNP Profile stored on the local file system. I even found a copy of GPNP Profile directly stored in OLR (in Oracle 12c release 2)
The Voting Files locations on ASM Disks are accessed by CSSD with well-known pointers in the ASM Disk headers and CSSD is able to complete initialization and start or join an existing cluster.
OHASD starts an ASM instance. The ASM instance uses special code to locate the contents of the ASM SPFILE ("how? you can read here"), if it is stored in a Disk group.
With an ASM instance operating and its Diskgroups mounted, access to Clusterware’s OCR is available to CRS.
OHASD then starts CRSD (ora.crsd)damon with access to the OCR in an ASM Diskgroup.
And thus Clusterware completes initialization and brings up other cluster managed resources defined in OCR.
Below you can find the simplified Clusterware Process Startup flow. The Chart has been taken from
I loved your post.Much thanks again. Fantastic.
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