Grid Infrastructure and RAC 12.2 New Features – a Recap

The following list illustrates the new 12.2 Oracle RAC and Grid Infrastructure. This is a personal list which “I believe to be the most interesting.” I apologize to the RAC Dev team if I left out any features.

Streamlined Grid Infrastructure Installation

12.2 Grid Infrastructure software is available as an image file for download and installation. The key objective of this feature was to enable a simpler and quicker installation of Grid Infrastructure. Administrators simply prep the system by creating a new Grid home directory, appropriate users, permissions and kernel settings. Once completed, Admins extract the image file into the newly-created Grid home, and execute the script to invoke setup wizard to register the Oracle Grid Infrastructure stack with Oracle inventory. This installation approach can be used for Oracle Grid Infrastructure for Cluster and Standalone Servers configurations. This new software installation will improve large scale deployment automation as well as deployment of customized images, Patch Set Updates (PSUs) and patches.

Real Application Clusters Reader Nodes

In 12.2, Oracle extended the capability of Flex Clusters by introducing Reader nodes. Reader nodes are Leaf nodes (in a Flex Cluster) that run read-only RAC database instances. The Reader nodes are not affected by RAC reconfigurations, caused by node evictions or other cluster node membership changes, as long as the Hub Node, to which it is connected, is part of the cluster. Reader Nodes allows users to create huge reader farms (up to 64 reader nodes per Hub Node), thus enabling massive parallel processing. In this architecture, updates to the read/write instances (running on Hub nodes) are immediately propagated to the read-only instances on the Leaf Nodes, where they can be used for online reporting or instantaneous queries. Users can create services to direct queries to read-only instances running on reader nodes.

Service-Oriented Buffer Cache Access

RAC Services, which are used to allocate and distribute workloads across RAC instances, are the cornerstone of RAC workload management. There is a strong relationship between a RAC Service, a specific workload, and the database object it accesses. With 12.2 RAC, a Service- oriented buffer cache feature was introduced to improve scale and performance, by optimizing instance and node-buffer cache affinity. This is done by caching or pre-warming instances with data blocks for objects accessed where a service is expected to run.

Twelve Days of 12.2

Server Weight-Based Node Eviction

When there is a spilt-brain, or when a node eviction decision must be made, traditionally the decision was based on age, or duration of the nodes, in the cluster; i.e., nodes with a large uptime in the cluster will survive. In 12.2 RAC, Server weight-based node eviction uses a more intelligent, tie-breaker mechanism to evict a particular node or a group of nodes from a cluster. The Server Weight-based node eviction feature introspects the current load on those servers as part of the decision. Two principle mechanisms, a system inherent automatic mechanism and a user input-based mechanism is used to offer and provide guidance.

Load-Aware Resource Placement

Load-aware resource placement, prevents overloading a server with more database instances than the server is capable of running. The metrics used to determine whether an application can be started on a given server, is based on the expected resource consumption of the application, as well as the capacity of the server in terms of CPU and memory. Administrators can define database resources such as CPU (cpu_count) and memory (memory_target) to Clusterware. Clusterware uses this information to place the database instances only on servers that meet a sufficient number of CPUs, amount of memory or both.

srvctl modify database -db testdb -cpucount 8 -memorytarget 64g

Hang Manager

The Hang Manager features first became available in 11gR1. In this initial version, Hang Manager evaluated and identified system hangs, then dumped the relevant information, “wait for graph,” into a trace file. In 12.2, Hang Manager takes action and attempts to resolve the system hang. An ORA-32701 error message is logged in the alert log to reflect the hang resolution. Hang Manager also runs in both single-instance and Oracle RAC database instances. With Hang Manager, it is constantly aware of processes running in reader nodes instances, and checks whether any of these processes are blocking progress on Hub Nodes to take action, if possible.

Separation of Duty for Administering RAC Clusters

12.2 RAC introduces a new administrative privilege called SYSRAC. This privilege is used by the Clusterware agent, and removes the need to use SYSDBA privilege for RAC administrative tasks, thus reducing the reliance on SYSDBA on production systems. Note, SYSRAC privilege is the default mode for connecting to the database by Clusterware agent; e.g, when executing RAC utilities such as SRVCTL.

Rapid Home Provisioning of Oracle Software

Rapid Home Provisioning enables you to create clusters, provision, patch, and upgrade Oracle Grid Infrastructure and Oracle Database homes. It also provisions 11.2 Clusters, applications, and middleware using Rapid Home Provisioning.

Extended Clusters

In 12.2 GI Administrators can create an extended RAC cluster across two, or more, geographically separate sites. Note, each site will include a set of servers with its own storage. If a site fails, the other site acts as an active standby. 12.2 Extended Clusters can be built on initial installation or be converted from an existing (non-Flex ASM) cluster, using the ConvertToExtended script.

De-support of OCR and Voting Files on Shared Filesystem

In Grid Infrastructure 12.2, the placement of Oracle Clusterware files: the Oracle Cluster Registry (OCR), and the Voting Files, directly on a shared file system is desupported. Only ASM or NFS is supported. If you need to use a supported shared file system, either a Network File System, or a shared cluster file system instead of native disk devices, then you must create Oracle ASM disks on supported network file systems that you plan to use for hosting Oracle Clusterware files before installing Oracle Grid Infrastructure. You can then use the Oracle ASM disks in an Oracle ASM disk group to manage Oracle Clusterware files. If your Oracle Database files are stored on a shared file system, then you can continue to use shared file system storage for database files, instead of moving them to Oracle ASM storage.