What is split brain in Oracle RAC?

Split brain syndrome occurs when the instances in a RAC fails to connect or ping to each other via the private interconnect, Although the servers are physically up and running and the database instances on these servers is also running.

What is split-brain situation?

Split brain syndrome, in a clustering context, is a state in which a cluster of nodes gets divided (or partitioned) into smaller clusters of equal numbers of nodes, each of which believes it is the only active cluster.

What is node eviction in Oracle RAC?

A node eviction is done when a heartbeat indicates that a node is not responding, and the evicted node is re-started so that it can continue to partiipate in the cluster. Reason for RAC node evictions. There are many reasons for a RAC node eviction.

What is Cache Fusion in Oracle RAC?

Oracle RAC Cache Fusion is simply where Oracle RAC transfers data blocks from the buffer cache of one instance to the buffer cache of another instance across the cluster interconnect. Transfers across this private network are in order of magnitude better than disk I/O activity and they help Oracle RAC performance.

What is OCR in Oracle RAC?

Oracle Cluster Registry (OCR) The OCR contains cluster and database configuration information for RAC and Cluster Ready Services (CRS) such as the cluster node list, and cluster database instances to node mapping, and CRS application resource profiles. The OCR is a shared file located in a cluster file system.

008 - How Node Membership Happens in RAC? - What is Voting Disk

What is difference between OCR and OLR in RAC?

ORACLE LOCAL REGISTRY(OLR) contains node-specific information required by OHASD . Every node has its own dedicated OLR file. (not shared between the nodes). As OCRs files are present in ASM diskgroup, While starting the CRS, it wont be able to Access OCR file to find the cluster resource information.

What is scan IP and VIP in Oracle RAC?

SCAN virtual IP addresses (VIPs) function like node VIPs. However, unlike node VIPs, SCAN VIPs can run on any node in the cluster. Clients (users or applications) that connect using a SCAN instead of a node VIP name or address do not have to update the list of node names or addresses in their local tnsnames.

What is GES and GCS in Oracle RAC?

The GCS and GES are integrated components of Real Application Clusters that coordinate simultaneous access to the shared database and to shared resources within the database and database cache. GES and GCS together maintain a Global Resource Directory (GRD) to record information about resources and enqueues.

What is OCR and voting disk in Oracle RAC?

The voting disk is a file that manages information about node membership, and the OCR is a file that manages cluster and Oracle RAC database configuration information. The Oracle Clusterware installation process creates the voting disk and the OCR on shared storage.

What is CR image in RAC?

CR Image: A consistent read (CR) block represents a consistent snapshot of the data from a previous point in time. Applying undo/rollback segment information produces consistent read versions.

What is heartbeat in Oracle RAC?

Answer: A heartbeat is a polling mechanism, similar to a ping, that monitors the availability of other servers in a RAC system. The heartbeat is a type of polling mechanism that is sent over the cluster interconnect to ensure that all RAC nodes are available. The heartbeat is part of the clusterware node monitoring.

What is IO fencing in Oracle RAC?

I/O fencing is a feature that prevents data corruption in the event of a communication breakdown in a cluster. To provide high availability, the cluster must be capable of taking corrective action when a node fails. In this situation, SF Oracle RAC configures its components to reflect the altered membership.

What happens when Ocssd fails?

COMMON CAUSES OF OCSSD EVICTIONS

It would take 30 consecutive missed checkins (by default – determined by the CSS misscount) to cause a node eviction. Problems writing to or reading from the CSS voting disk. If the node cannot perform a disk heartbeat to the majority of its voting files, then the node will be evicted.

What is split-brain in SQL cluster?

Split brain is a state of a server cluster where nodes diverge from each other and have conflicts when handling incoming I/O operations. The servers may record the same data inconsistently or compete for resources.

What is the purpose of using split brain DNS?

Split-brain DNS ensures that when users at the office on the local network type in www.mydomain.com, the DNS record returned contains the internal private IP address of the website you've set up, but when users away from the office's local network try to access www.mydomain.com, the DNS record returned contains the ...

Why does split-brain happen?

The primary cause of split-brain syndrome is intentional severing of the corpus callosum, partially or completely, through a surgical procedure known as corpus callosotomy.

How do I find my master node in RAC?

Why does Oracle RAC have odd number voting disk?

Why we need to keep odd number of voting disks ? Oracle expects that you will configure at least 3 voting disks for redundancy purposes. You should always configure an odd number of voting disks >= 3. This is because loss of more than half your voting disks will cause the entire cluster to fail.

What is Oracle GCS?

Oracle Global Customer Support (GCS) is a global operation. GCS follows formal security practices when performing software, hardware, and cloud technical support for its customers. These security practices are designed to preserve the security posture of our customers.

What processes are required in RAC?

What is Oracle LMON?

LMON (Lock MONitor) is an Oracle background process created when you start a database instance in RAC mode. The LMON process manages global locks and resources. It is also callded Global Enqueue Service Monitor.

Why are there 3 SCAN listeners in Oracle RAC?

It reduces connectivity time for application or web based end users. Normally 3 SCANs are capable enough to handle hundreds of new connections in a span of few seconds. Still if you feel that default 3 SCAN listeners are not enough for your environment then you have an option to add few more scan listeners.

Why does Oracle RAC have 3 SCAN?

As we know that the recommended value for SCAN ip using DNS/GNS is 3 SCAN IPS and this creates 3 SCan listeners randomly on the nodes. If we have a 5 node cluster then how many SCAN IPs are recommended.

How many IPS are there in RAC?

So in summary, there are at minimum 2 physical network devices, and 3 IP addresses per RAC node. Oracle 11g RAC introduces the concept of the single client access name, or SCAN. The idea behind this is that applications/client will only connect to a single domain name when connecting to a RAC database.