Is it possible to use OLR without OCR

 Answer is No, interesting and thought provoking 

This is introduced in Oracle 11gR2 which will have all the resource information about the node and it can't shared across nodes.

Why Oracle introduced OLR in the sense of, while starting the clusterware some of the resources needs to be started first. Before 11gR2, everything stored in OCR which is residing in OS files. But from 11gR2, OCR and voting disk Saved in ASM. So, to start the clusterware, need to start the ASM first. Without knowing resource information Oracle can't start ASM. So for that reason, Oracle is maintaining Local registry to start the resources and start the clusterware.

If OLR is missing/corrupted, the clusterware won't get started.

To answer this, Oracle introduced a component called OLR.

Ø It is the first file used to startup the clusterware when OCR is stored on ASM.

Ø Information about the resources that needs to be started on a node is stored in an OS file called ORACLE LOCAL REGISTRY (OLR).

Ø Since OLR is an OS file, it can be accessed by various processes on the node for read/write irrespective of the status of cluster (up/down).

Ø When a node joins the cluster, OLR on that node is read, various resources, including ASM are started on the node.

Ø Once ASM is up, OCR is accessible and is used henceforth to manage all the cluster nodes. If OLR is missing or corrupted, clusterware can’t be started on that node.

Oracle Local Registry is OCRs local counterpart. It stores information about the local node only, mainly related to the OHASd

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