At a very high level, RAC architecture consists of these components:
- Physical nodes or hosts
- Physical interconnects and interconnect protocols
- Oracle Clusterware
- Oracle instances and cache fusion
- Shared disk system
- Clustered file system, raw devices, network file system, Automatic Storage Management
- Network services
- Workload Management Services - Virtual IP configuration
- Physical nodes or hosts.
- Physical interconnects and interconnect protocols.
- Oracle Clusterware.
- Oracle instances and cache fusion.
- Shared disk system.
- Clustered file system, raw devices, network file system, Automatic Storage Management.
- Network services.
What is Oracle RAC option with Oracle Database?
The Oracle RAC option with Oracle Database enables you to cluster Oracle databases. Oracle RAC uses Oracle Clusterware for the infrastructure to bind multiple servers so they operate as a single system. Oracle Clusterware is a portable cluster management solution that is integrated with Oracle Database.
What is shared everything in Oracle RAC?
An Oracle RAC database is a shared everything database. All data files, control files, SPFILEs, and redo log files in Oracle RAC environments must reside on cluster-aware shared disks, so that all of the cluster database instances can access these storage components.
What is Oracle RAC Clusterware?
Oracle Clusterware is a required component for using Oracle RAC that provides the infrastructure necessary to run Oracle RAC. Oracle Clusterware also manages resources, such as Virtual Internet Protocol (VIP) addresses, databases, listeners, services, and so on.
What is a view in Oracle RAC?
Any one instance's database view is nearly identical to any other instance's view in the same Oracle RAC database; the view is a single system image of the environment. Each instance has a buffer cache in its System Global Area (SGA).
What is the purpose of Oracle RAC?
Oracle Real Application Clusters (RAC) allow customers to run a single Oracle Database across multiple servers in order to maximize availability and enable horizontal scalability, while accessing shared storage.
What is Oracle RAC architecture?
The Oracle RAC option with Oracle Database enables you to cluster Oracle databases. Oracle RAC uses Oracle Clusterware for the infrastructure to bind multiple servers so they operate as a single system. Oracle Clusterware is a portable cluster management solution that is integrated with Oracle Database.
What are services in Oracle RAC?
In Oracle RAC, Oracle services are designed to be continuously available with workloads shared across one or more instances. The Oracle RAC high availability framework maintains service availability by storing the configuration information for each service in the Oracle Cluster Registry (OCR).
How many nodes are in RAC cluster?
Oracle RAC 11g supports up to 100 nodes.
What is a cluster in Oracle RAC?
Oracle Real Application Clusters (RAC) allow customers to run a single Oracle Database across multiple servers in order to maximize availability and enable horizontal scalability, while accessing shared storage.
What is OLR and OCR in RAC?
Oracle Cluster Registry (OCR) and Oracle Local Registry (OLR) are two very important components of a Grid Infrastructure that help manage the cluster resources. In a nutshell, OCR is used by CRSd and OLR by the OHASd.
What is load balancing in Oracle RAC?
Services coordinate their sessions by registering their workload, or the amount of work they are currently handling, with the local listener and the SCAN listeners.
What is high availability service in Oracle RAC?
OHAS is implemented via a new daemon process which is called ohasd on the OS layer, and the 11g documentation notes that this Oracle High Availability Services Daemon (OHASD) anchors the lower part of the Oracle Clusterware stack, which consists of processes that facilitate cluster operations in RAC databases.
What is available node and preferred node in RAC?
In Oracle Real Application Clusters (RAC) setup, you can specify the preferred nodes on which the backup operation will be performed. If you do not specify the preferred node, SnapCenter automatically assigns a node as the preferred node and backup is created on that node.
What are RAC nodes?
Oracle Real Application Clusters (RAC) One Node is an option to the Oracle Database Enterprise. Edition that was introduced with Oracle Database 11g Release 2. It provides enhanced high availability. for single instance Oracle Databases, protecting them from both, planned and unplanned downtime.
What is RAC configuration?
Oracle Real Application Cluster (RAC) is a "share-everything" database architecture that can provide high availability and load balancing. A typical configuration for an Oracle RAC contains two or more Oracle RAC nodes that are clustered together and share the same storage.
Does Oracle RAC require shared storage?
You can only use Direct NFS Client to store Oracle Database files. To install Oracle RAC on Windows using Direct NFS Client, you must have access to a shared storage method other than NFS for the Oracle Clusterware files.
How does RAC database work?
Oracle RAC databases generally have two or more database instances that each contain memory structures and background processes. An Oracle RAC database has the same processes and memory structures as a noncluster Oracle database and additional processes and memory structures that are specific to Oracle RAC.
What is the difference between Oracle RAC and Exadata?
Difference Between Exadata and Oracle Database Appliance The database layer consists of Sun servers and runs Oracle 11gR2 software and normally Oracle RAC is deployed on database node. The database layer uses ASM to map to the storage layer.
What is Oracle Grid and RAC?
RAC is Oracle's specific implementation of [potentially] many computers working together to manipulate one database. So I conclude that RAC is Oracle's implementation of grid computing for the database.
Is Oracle RAC supported on AWS?
You can now deploy scalable Oracle Real Application Clusters (RAC) on Amazon EC2 using the recently-published tutorial and Amazon Machine Images (AMI) on AWS Marketplace.
What storage system is used for Oracle RAC?
Oracle recommends ASM as a storage option for Oracle RAC environments. Cluster File System One or more cluster file systems can be used to hold all Oracle RAC datafiles. Oracle recommends the use of the Oracle Cluster File System (OCFS).
Why use a voting disk in Oracle RAC?
Oracle RAC uses the voting disk to determine the active instances of the cluster , and inactive instances are evicted from the cluster. Because the voting disk plays a vital role, you should mirror it. If Oracle mirroring is not used for the voting disk, external mirroring should be used.
What is Oracle Clusterware?
It is Oracle Clusterware that manages entities such as databases, listeners, services, and virtual IP addresses, which are referred to as resources in Oracle Clusterware parlance. Oracle Clusterware uses processes or services that run on the individual nodes of the cluster to provide the high availability capabilities for a RAC database. It enables nodes to communicate with each other and forms the cluster that makes the nodes work as a single logical server.
What is scalable storage?
Scalable shared storage is a critical component of an Oracle RAC environment. Traditionally, storage was attached to each individual server using SCSI (Small Computer System Interface) or SATA (Serial ATA) interfaces local to the hosts. Today, more flexible storage is popular and is accessible over storage area networks (SANs) or network-attached storage (NAS) using regular Ethernet networks. These new storage options enable multiple servers to access the same set of disks through a network, simplifying provisioning of storage in any distributed environment. SANs represent the evolution of data storage technology to this point.
What is ASM in Oracle?
Automatic Storage Management (ASM) ASM is a portable, dedicated, and optimized cluster file system for Oracle database files. ASM is the only supported storage if you use Oracle Standard Edition with Oracle RAC. Oracle recommends ASM as a storage option for Oracle RAC environments.
Where is the OCR file located?
Oracle stores the location of the OCR file in a text file called ocr.loc, which is located in different places depending on the operating system. For example, on Linux-based systems the ocr.loc file is placed under the /etc/oracle directory, and for UNIX-based systems the ocr.loc is placed in /var/opt/oracle.
Can you use multiple file systems in Oracle RAC?
The choice of file system is critical for Oracle RAC deployment. Traditional file systems do not support simultaneous mounting by more than one system. Therefore, you must store files in either raw volumes without any file system or on a file system that supports concurrent access by multiple systems.
How to run RAC in Oracle?
To run Oracle RAC in configurations with different versions of Oracle Database in the same cluster, you must first install Oracle Grid Infrastructure, which must be the same version, or higher, as the highest version of Oracle Database that you want to deploy in this cluster. For example, to run an Oracle RAC 12 c database and an Oracle RAC 18c database in the same cluster, you must install Oracle Grid Infrastructure 18c. Contact My Oracle Support for more information about version compatibility in Oracle RAC environments.
How many instances does Oracle RAC have?
An Oracle RAC database can have several instances, all of which access one database. All database instances must use the same interconnect, which can also be used by Oracle Clusterware. Oracle RAC databases differ architecturally from non-cluster Oracle databases in that each Oracle RAC database instance also has:
What is a reader node in Oracle?
Reader nodes are instances of an Oracle RAC database that provide read-only access, primarily for reporting and analytical purposes.
What to do before installing Oracle RAC?
Before installing the Oracle RAC database software and creating respective databases, decide on the management style you want to apply to the Oracle RAC databases, as described in "Overview of Server Pools and Policy-Managed Databases" .
What is Oracle Clusterware?
Oracle Clusterware is a required component for using Oracle RAC that provides the infrastructure necessary to run Oracle RAC. Oracle Clusterware also manages resources, such as Virtual Internet Protocol (VIP) addresses, databases, listeners, services, and so on.
What is a non cluster Oracle database?
Non-cluster Oracle databases have a one-to-one relationship between the Oracle database and the instance. Oracle RAC environments, however, have a one-to-many relationship between the database and instances. An Oracle RAC database can have several instances, all of which access one database. All database instances must use the same interconnect, which can also be used by Oracle Clusterware.
Where is Oracle RAC located?
Traditionally, an Oracle RAC environment is located in one data center. However, you can configure Oracle RAC on an Oracle Extended Cluster, which is an architecture that provides extremely fast recovery from a site failure and allows for all nodes, at all sites, to actively process transactions as part of a single database cluster. In an extended cluster, the nodes in the cluster are typically dispersed, geographically, such as between two fire cells, between two rooms or buildings, or between two different data centers or cities. For availability reasons, the data must be located at both sites, thus requiring the implementation of disk mirroring technology for storage.
Why should we use Oracle RAC?
That shared-everything subsystem is actually made sure that OLTP workloads will be highly steady regardless if there are numerous Oracle RAC nodes.
What is method in Oracle RAC?
A method is simply recognized for Oracle RAC, whenever every layer will be reinforced.
What is RAC in SGA?
RAC benefits Cache Fusion (a quick dedicated backplane the nodes use to connect that one another) that allows the cluster users to share data that may be cached inside the SGA. This means the entire SGA with the whole cluster (and therefore the quantity of data which can be cached) is really nearly the sum of the SGA’s individual’s nodes.
What is Oracle redo thread?
Every Oracle instance creates a unique set of online redo logs, which will often consist of mirrored online redo logs, based on the settings. All of the categories owned by an individual instance are known as internets redo thread, recognized by their unique amount.
What is Oracle instance?
Oracle Instance is a Memory and Process handler. Oracle Databases is a combination of 3 different types of files mainly control files, redo log files and database files. All control files, online redo log files, and database files are stored on the cluster file system or shared raw devices, which can be accessed by all computers in the cluster.
What is a DBA in Oracle?
Qualified Oracle Database Administrators (DBA) are usually in demand on the market. Likewise, being a company’s database keeps growing we have a large requirement for people who can manage, maintain as well as, develop databases since arranged up/designs, troubleshooting challenges and setting guidelines to increase efficiency.
Can you add additional nodes to Oracle cluster?
If the extra processing capacity is required, clients can also add additional nodes rather than changing their accessible servers. The only requirement is that servers in the cluster need to work a similar operating system as well as the same version of Oracle. They cannot need to be of identical capability.
How to acquire a lock in Oracle?
Otherwise, it waits on the Convert Q until the resource becomes available. When a lock is released or converted, the converters run the check algorithm to see if they can be acquired.
What is CGS in Oracle?
One of the key “hidden” or lesser-known components of OPS is Cluster Group Services (CGS). CGS had some OSD components (such as the node monitor interface), and the rest of it is the GMS part built into the Oracle kernel. CGS holds a key repository used by the DLM for communication and network-related activities. This layer in the Oracle 8 i kernel (and beyond) provides the following key facilities without which an OPS database cannot operate:
What is parallel cache management?
Parallel Cache Management (PCM) means that the coordination and maintenance of data blocks occur within each data buffer cache (of an instance) so that the data viewed or requested by users is never inconsistent or incoherent. The access to data is controlled via the PCM framework using data blocks with global coordinated locks. In simple terms, PCM ensures that only one instance in a cluster can modify a block at any given time. Other instances have to wait.
When to use group based locking?
Groups are used when group-based locking is used. This is preferred particularly when MTS is involved, and when MTS is used the shared services are implicitly unavailable to other sessions when locks are held. From Oracle 9 i onward, process-based locking no longer exists. Oracle 8 i OPS (and later) uses group-based locking irrespective of the kind of transactions. As mentioned, a process within a group identifies itself with the XID before asking Oracle for any transaction locks.
Is IDLM the same as Oracle?
IDLM lock modes and Oracle lock modes are not identical, although they are similar. In OPS, locks can be local or global, depending on the type of request and operations. Just as in a single instance, locks take the form
Does Oracle use a row lock?
In contrast, transactions do not release row locks until changes to the rows are either committed or rolled back. Oracle uses internal mechanisms for concurrency control to isolate transactions so modifications to data made by one transaction are not visible to other transactions until the transaction modifying the data commits. The row lock concurrency control mechanisms are independent of parallel cache management: concurrency control does not require PCM locks, and PCM lock operations do not depend on individual transactions committing or rolling back.
Why is Oracle RAC important?
Oracle RAC help with these requirements . In fact, the scalability features in Oracle RAC make it possible to start with a smaller footprint and scale out as needed resulting in massive savings as customers do not need to provision a large environment upfront in anticipation of future requirements. Figure 3 below depicts the horizontal scale out of Oracle RAC running a SAP sales and distribution (SD) module benchmark.
What is a reconfiguration in Oracle RAC 19C?
In Oracle RAC 19c, smart reconfiguration reduces the impact of service disruption from both planned and unplanned operations utilizing features such as Recovery Buddy and Service Isolation resulting in up to 4 times faster reconfiguration than previous releases.
How does recovery buddy work in Oracle RAC?
Recovery Buddy feature greatly reduces the time sessions have to wait during reconfiguration. In prior releases, Oracle RAC instances identified and recovered the changes made by the failed instance by reading the redo logs. The surviving instances have to wait until the changes from the failed instance are read and applied. However, reading these changes from storage is time consuming. Recovery Buddy feature optimizes this by allocating a Buddy Instance for every RAC Node. These Buddy instances track the block changes in the local SGA in a hash table. This allows recovery to proceed faster as the changes are read from the hash table instead of reading from storage. In Oracle RAC 19c, the buddy instance gets the necessary recovery locks to be applied in batch mode instead of requesting locks one at a time resulting in faster recovery.
What is Oracle Clusterware?
Oracle Clusterware is the technology that transforms a server farm into a cluster. Oracle Clusterware is a complete, free-of-charge clustering solution that can be used with Oracle RAC, RAC One Node and even Single instance Oracle databases. Oracle Clusterware provides node membership, node fencing and optimal resource placement.
What is Oracle ASM?
Oracle Automatic Storage Management (ASM) is the recommended volume manager that can be used for both Oracle RAC and single instance Oracle Databases. Oracle ASM simplifies storage management through the principle of stripe-and-mirror-everything (SAME). Intelligent mirroring capabilities allow administrators to define 2- or 3-way mirrors to protect vital data. When a read operation identifies a corrupt block on a disk, Oracle ASM automatically relocates the valid block from the mirrored copy to an uncorrupted portion of the disk.
What is Oracle Node Weighting?
Oracle Node Weighting feature improves the algorithm used to choose the node(s) to be evicted during a node eviction when the split brain results in a cluster to be split into equal half’s. In the past, the candidate node to be evicted was chosen based on the node number. In Oracle 19c, this algorithm is further improved as we consider several additional factors including the criticality of workloads that are currently running, singleton services and additional secondary failures. This feature does not require any manual intervention but DBA’s can optionally configure a node or service to be marked critical based on business needs. This optional step can be used to configure criticality for a specific server that has say more CPU or memory than other servers in the cluster. If all
Is Oracle a trademark?
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