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[TechTarget China original] this article is the third in a series of new features of Oracle Database 12c. The author will give an extensive introduction to the new and improved aspects of clustering, ASM and RAC databases. Related reading: summary of new features of Oracle database 12c (1), new features of Oracle database 12c (2), new features of Oracle database 12c (4)

The third part includes:

1. Enhancements in ASM

two。 Enhancements to grid infrastructure

3. Enhancement of Oracle RAC

1. Enhancements in automatic Storage Management (ASM)

Flex ASM

In a typical grid infrastructure installation environment, each node runs its own instance of ASM as a storage container for the database running on this node. However, there is a corresponding risk of single point of failure in this setting. For example, if the ASM instance on this node fails, all databases and instances running on this node are affected. To avoid a single point of failure of ASM instances, Oracle 12c provides a feature called Flex ASM. Flex ASM is a different concept and architecture, and only a small number of ASM instances need to run on some servers in the cluster. When an ASM instance on one node fails, the Oracle cluster automatically starts an alternative ASM instance on a different node to enhance availability. In addition, this setting provides ASM instance load balancing capabilities for instances running on this node. Another advantage of Flex ASM is that it can be configured on a separate node.

When the Flex Cluster option is selected as the first part of the cluster installation environment, the Flex ASM configuration is automatically selected due to the requirements of Flex Cluster. Traditional clusters are also applicable to Flex ASM. When you decide to use Flex ASM, you must make sure that the required network is available. You can choose the Flex ASM storage option as part of the cluster installation environment, or use ASMCA to enable Flex ASM in a standard cluster environment.

The following command shows the current ASM mode:

$. / asmcmd showclustermode

$. / srvctl config asm

Or connect to the ASM instance and query the INSTANCE_TYPE parameter. If the output value is ASMPROX, then Flex ASM is already configured.

Relaxation of ASM storage restrictions

The ASM storage hard limit has increased significantly in terms of the maximum ASM disk group and disk size. ASM supports 511 ASM disk groups in 12c R1 and 63 in 11g R2. Similarly, this number has now been increased to 32 PB compared to the disk size of 20 PB in 11g R2.

Optimization of ASM equalization operation

The new EXPLAIN WORK FOR statement in 12c is used to measure the amount of work required for a given ASM equalization operation and to enter the result in the V$ASM_ESTIMATE dynamic view. Using this dynamic view, you can adjust the POWER LIMIT statement to improve the rebalance operation. For example, if you want to measure the amount of work required to add a new ASM disk, you can use the following command before actually performing a manual equalization operation:

SQL > EXPLAIN WORK FOR ALTER DISKGROUP DG_DATA ADD DISK data_005

SQL > SELECT est_work FROM V$ASM_ESTIMATE

SQL > EXPLAIN WORK SET STATEMENT_ID='ADD_DISK' FOR ALTER DISKGROUP DG_DATA AD DISK data_005

SQL > SELECT est_work FROM V$ASM_ESTIMATE WHERE STATEMENT_ID = 'ADD_DISK'

You can adjust the POWER limits according to the output from the dynamic view to improve the equalization operation.

ASM disk cleanup

In an ASM disk group, the new ASM disk cleanup operation is divided into normal or highly redundant levels, which can detect logical data corruption on all disks in the ASM disk group, and can automatically repair logical corruption. If logical data corruption is detected, ASM mirrored disks are used. Disk cleanup can be performed on a disk group, a specific disk, or a file so that its impact can be minimized. The following demonstrates the disk cleanup scenario:

SQL > ALTER DISKGROUP dg_data SCRUB POWER LOW:HIGH:AUTO:MAX

SQL > ALTER DISKGROUP dg_data SCRUB FILE'+ DG_DATA/MYDB/DATAFILE/filename.xxxx.xxxx'

REPAIR POWER AUTO

Active session History of ASM (ASH)

The V$ACTIVE_SESSION_HISOTRY dynamic view can now also provide sampling of active sessions for ASM instances. However, the use of diagnostic packages is restricted by licensing.

two。 Enhancements to grid (Grid) infrastructure

Flex cluster

Oracle 12c supports two types of configurations during cluster installation: traditional standard clusters and Flex clusters. In a traditional standard cluster, all the nodes in the cluster are closely integrated with each other, interact through the private network, and have direct access to storage. On the other hand, Flex clusters introduce two types of nodes between Hub and Leaf node structures. The nodes assigned in Hub are similar to traditional standard clusters. They are interconnected to each other through private networks and have direct read and write access to storage. Unlike Hub nodes, Leaf nodes do not need to access the underlying storage directly; instead, they access storage and data through Hub nodes.

You can configure up to 64 Hub nodes, and Leaf nodes can have more. In an Oracle Flex cluster, there is no need to configure a Leaf node to have a Hub node, while without a Hub node, a Leaf node would not exist. For a single Hub node, you can configure multiple Leaf nodes. In an Oracle Flex cluster, only Hub nodes directly access OCR and Voting disks. This is a great feature when you are planning a large-scale clustered environment. This series of settings will greatly reduce interconnection congestion and provide space for traditional standard clusters to expand the cluster.

There are two ways to deploy Flex clusters:

1. Deploy when configuring a new cluster

two。 Upgrade a standard cluster mode to a Flex cluster

If you are configuring a completely new cluster, you need to select the type of cluster configuration in step 3, select the configure a Flex cluster option, and then you need to classify the Hub and Leaf nodes in step 6. For each node, select whether the corresponding role is Hub or Leaf, and the virtual hostname is optional.

Converting a standard cluster mode to Flex cluster mode requires the following steps:

1. Use the following command to get the current state of the cluster:

$. / crsctl get cluster mode status

two。 Execute the following command as the root user:

$. / crsctl set cluster mode flex

$. / crsctl stop crs

. / crsctl start crs-wait

3. Change the node role according to the design:

$. / crsctl get node role config

$. / crsctl set node role hub | leaf

$. / crsctl stop crs

. / crsctl start crs-wait

Note:

You can't go back to the standard cluster mode from Flex. Changing the cluster node mode requires the cluster stack to stop and ensure that the GNS is configured with a fixed VIP.

OCR backups in ASM disk groups

For 12c Magi OCR can now be backed up in the ASM disk group. This simplifies access to OCR backup files through all nodes. To prevent OCR recovery, you don't have to worry about which node the latest backup of OCR is on. The latest backup stored in ASM can be easily identified from any node and the restore can be easily performed.

The following demonstrates how to set the ASM disk group to the OCR backup location:

$. / ocrconfig-backuploc + DG_OCR

Support for IPv6 protocol

Oracle supports IPv6 network protocol configuration for 12c Oracle. You can now configure public or private network interfaces on IPv4 or IPv6, however, you need to make sure that the same IP protocol is used on all nodes in the cluster.

3. Enhancement of RAC database

What-if command evaluation

With srvctl using the new What-if command to evaluate options, you can now determine the impact of running this command. This newly added command to srvctl can be simulated without actually executing it or making any changes to the current system. This is especially useful when you want to make changes to an existing system but the results are uncertain. In this way, this command provides the effect of making changes. The-eval option can also be used through the crsctl command.

For example, if you want to know what happens when you stop a particular database, you can use the following example:

. / srvctl stop database-d MYDB-eval

. / crsctl eval modify resource-attr "value"

Improvement of srvctl

There are also some new features for the srvctl command. The following demonstrates how to use these new features to stop or start a database or instance resource on a cluster.

Srvctl start database | instance-startoption NOMOUNT | MOUNT | OPEN

Srvctl stop database | instance-stopoption NOMOUNT | MOUNT | OPEN

In the fourth article in this series, the author will focus on the most important developer features in Oracle Database 12c.

Original link: http://www.searchdatabase.com.cn/showcontent_75748.htm

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