Features introduced by Oracle 11g ASM

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Features introduced by Oracle 11g ASM

1.1 new features introduced by 11g ASM that affect Management
The following features will not be supported when the 10G version of ASM is maintained. However, most features have little impact on ASM maintenance.

1.1.1 Fast synchronization (ASM Fast Mirror Resync)
When a short DISK path is faulty, it takes a lot of time to restore the remainder of the asm disk group, especially when such a restoration operation requires the entire disk group to be redeployed. The new feature of ASM fast disk re-synchronization can significantly reduce the time required to re-synchronize a bad disk. When you replace the bad disk, ASM can quickly synchronize the extent of the ASM disk.

Any problem that temporarily makes the disk group unavailable is considered to be a temporary failure, which can be recovered after ASM quickly resynchronizes new features. Disk path failure, such as interface line problems, host adapter problems, disk controller problems, or disk power problems can cause transient failure. By default, when a disk is offline, ASM will immediately remove it. The ASM fast synchronization function is enough to record all the changes in the disk's upper zone during the offline period of the offline disk. When the disk is repaired or brought online again, during this period, the changed extent can be quickly synchronized to those disks that have just expired.

You can set the DISK_REPAIR_TIME attribute so that the failed disk will not be reorganized during the time when it is repaired or brought online again. This time can be measured in minutes (m or M) or hours (h or H). If you do not specify the time unit, the default time unit is hour. If DISK_REPAIR_TIME is not set, the default value is 3.6 hours. Note that this default value applies when the disk is set to offline mode and the operation statement does not have the drop after clause. In most cases, the default attribute value of DISK_REPAIR_TIME in 3.6 hours should be appropriate.

Note:

With this new feature, the compatibility of the ASM disk group must be set to 11.1 or higher.

Example:

Create diskgroup asmdskgrp1 DISK '/dev/raw /*'

Set attribute 'compatible. rdbms '= '11. 1', 'compatible. asm' = '11. 1 ';

Only when the disk that contains the offline disk is attached again, the elapsed time (after the disk is set to offline mode) increases, the REPAIR_TIME column of V $ ASM_DISK shows the time remaining before the offline disk is deleted (unit: seconds). When the specified time arrives, ASM deletes the disk, you can use the alter diskgroup disk offline statement with drop after to overwrite this attribute.

Note:

Drop after is also a new feature of 11g.

If a disk operated by the alter diskgroup set attribute DISK_REPAIR_TIME operation contains offline disks, this ATTRIBUTE takes effect only for non-Offline disks currently.

When an offline disk is offline for the second time, the elapsed time is reset and the computation starts again. If the disk is dropped AFTER at another time, the previous value will be overwritten and the new value will take effect. You cannot use the alter diskgroup drop disk statement to delete an offline DISK. In this case, an error is returned. If the disk cannot be repaired at a certain time, for example, when the disk needs to be deleted before DISK_REPAIR_TIME arrives, you can run the OFFLINE statement with the drop after clause again, drop after specifies 0 h or 0 M, which means to delete immediately.

You can use alter diskgroup to set the DISK_REPAIR_TIME attribute of the disk group, which can be minute or hour, for example, 4.5 hours or 270 minutes. For example:

Alter diskgroup dg01 set attribute 'disk _ repair_time '= '4. 5h'

Alter diskgroup dg01 set attribute 'disk _ repair_time '= '70m'

After you fix the DISK, run the alter diskgroup disk online SQL statement to restore the DISK group to the ONLINE status. All new read/write operations can be performed normally, this statement also triggers the re-synchronization of extent changed during the disk service period from redundant data in the disk group to those disks that have just expired.

1.1.2 ASM rolling upgrade
In Oracle11g and later versions, you can set the ASM cluster to the "rolling upgrade" mode to allow different versions of ASM nodes to work together. In the rolling upgrade mode, each node can be upgraded or patched independently without affecting the database usage. This greatly improves the normal running time of the database. Note that you can only perform "rolling upgrade" for ORACLE11g and later versions. In other words, you cannot use this function to upgrade ORACLE10g databases to 11G.

Before performing a rolling upgrade, make sure your environment is ready. For example, if you use the ORACLE Clusterware software, you must complete the upgrade to the next version that meets the requirements before rolling the upgrade. Of course, you should also use the rolling method when upgrading Clusterware to ensure higher stability and the maximum normal running time.

Before patching or upgrading the ASM software at a node, you must set the ASM cluster to the rolling upgrade mode, which allows you to start upgrading and operating your environment in multiple software versions, the statement is as follows:

Alter systemstart rolling migration to number;

Number is composed of the version number, Release number, update number, port release number, and port UPDATE number, separated by commas (,), for example, 11.2.0.0.0.

When running this statement, the instance checks whether the number you specified is compatible with the installed software version. After the upgrade, the following operations are sufficient for the ASM instance:

L mount and detach a disk

L open, close, and re-set the size and delete of database files

L restrict access to the views and packages provided by ORACLE. All Global Views are invalid.

After the rolling upgrade starts, you can upgrade the software by dropping any ASM instance. After the upgraded ASM instance is started, it is automatically added to the ASM cluster. After all the instances in the cluster are upgraded to the latest software version, you can end the rolling upgrade mode.

If a disk is offline during rolling upgrade of the ASM instance, the disk remains offline until the upgrade is completed, the disk deletion record is stopped when the ASM cluster returns to normal mode.

If a problem occurs after the upgrade, you can use the same process to roll back the node software to the previous version. The cluster has a data reorganization operation, and the upgrade will fail. Therefore, you must wait until the data reorganization operation is complete to start rolling upgrade. In addition, as long as one node in the cluster is active, the rolling upgrade status is retained.

If a new ASM instance is added when a cluster is performing rolling upgrade, the new instance is notified that the cluster is in rolling upgrade mode, you can use the following SQL statement to query the status of the ASM cluster environment:

SELECTSYS_CONTEXT ('sys _ cluster_properties ', 'Cluster _ state') from dual;

If all the instances in the ASM cluster are stopped, the instance will be out of the rolling upgrade mode when any ASM instance is restarted. To upgrade an instance after it is restarted, you must restart the rolling upgrade operation.

After the rolling upgrade is complete, run the following SQL:

Alter systemstop rolling migration;

After this statement is issued, ORACLE performs the following operations:

L check whether the software versions of all the members of the ASM cluster are the same. If one or more instances run in different software versions, this statement reports an error and the cluster continues to be in the rolling upgrade mode.

L remove all instances of the cluster from the rolling upgrade mode, and the cluster starts to work fully.

L if the ASM_POWER_LIMIT parameter is set to allow data re-sorting, the data re-sorting operation that is blocked due to rolling upgrade will start again.

 

1.1.3 add SYSASM permissions and OSASM operating system user groups to the ASM Administrator
In ORACLE10g, ORACLE does not customize the corresponding roles for the ASM administrator. The ASM administrator manages the tasks with the SYSDBA role, in actual work, the ASM administrator and the database administrator may be two or several different people, and the permission definition is relatively unclear. 11g this new feature introduces SYSASM this new permission aims to clear the interfaces between the ASM administrator and the database administrator, prevent unauthorized operations, and make the ASM administrator better manage the ASM.

This new feature also adds an OSASM user group to the operating system. The OSASM group is specially designed for ASM and can be authorized by the operating system, the authorized members of this group have the SYSASM permission for local connection and can perform full-Permission ASM management with the SYSASM role. At first, only the ASM installer is a member of this group. In subsequent work, you can add new users to the OSASM user group so that new users have all permissions for ASM management.

It should be noted that in ORACLE11gRelease 1, members of the OSDBA Group of the system can still connect to and manage ASM instances according to SYSDBA permissions, however, we believe that users with SYSDBA permissions in subsequent versions will not be authorized to manage the ASM instance.

1.1.4 new ASM command line (ASMCMD) commands and options
ASMCMD has the following four new commands: lsdsk, md_backup, md_restore, and remap. In addition, you can use the ls and lsdg commands with new options. The following describes the four new ASM commands:

Lsdsk-whether or not there is an ASM real column running, this command can list information about the ASM disk. This command is useful when the system administrator or storage administrator wants to check which disks are used by the ASM instance.

The md_backup and md_restore commands allow you to re-create an existing disk group with the same disk path, disk name, failure group, attributes, template, and directory structure alias. You can use md_backup to back up the disk group environment and use mk_restore to restore the corresponding disk group when a problem occurs.

Remap-you can use this command to Remap or reply to Bad blocks in the ASM disk in normal and high redundancy modes. ASM reads the corresponding blocks in a copy of the ASM image, and write these blocks back to an alternative position in the disk group.

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