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Using the Oracle ASM Cluster File System (Oracle ACFS) on Linux, Part Three

Expert Oracle Tips by Jeff Hunter

March 21, 2011

 
This article continues on with
an exploration of ACFS snapshots and managing ACFS and then concludes this three part series on using ACFS on Linux.

ACFS Snapshots

Oracle ASM Cluster File System includes a feature called snapshots. An Oracle ACFS snapshot is an online, read-only, point in time copy of an Oracle ACFS file system. The snapshot process uses Copy-On-Write functionality which makes efficient use of disk space. Note that snapshots work at the block level instead of the file level. Before an Oracle ACFS file extent is modified or deleted, its current value is copied to the snapshot to maintain the point-in-time view of the file system. (Note: When a file is modified, only the changed blocks are copied to the snapshot location which helps conserve disk space.)

Once an Oracle ACFS snapshot is created, all snapshot files are immediately available for use. Snapshots are always available as long as the file system is mounted. This provides support for online recovery of files inadvertently modified or deleted from a file system. You can have up to 63 snapshot views supported for each file system. This provides for a flexible online file recovery solution which can span multiple views. You can also use an Oracle ACFS snapshot as the source of a file system backup, as it can be created on demand to deliver a current, consistent, online view of an active file system. Once the Oracle ACFS snapshot is created, simply backup the snapshot to another disk or tape location to create a consistent backup set of the files. (Note: Oracle ACFS snapshots can be created and deleted on demand without the need to take the file system offline. ACFS snapshots provide a point-in-time consistent view of the entire file system which can be used to restore deleted or modified files and to perform backups.)

All storage for Oracle ACFS snapshots are maintained within the file system which eliminates the need for separate storage pools for file systems and snapshots. As shown in the next section, Oracle ACFS file systems can be dynamically re-sized to accommodate addition file and snapshot storage requirements.

Oracle ACFS snapshots are administered with the acfsutil snap command. This section will provide an overview on how to create and retrieve Oracle ACFS snapshots.

Oracle ACFS Snapshot Location

Whenever you create an Oracle ACFS file system, a hidden directory is created as a sub-directory to the Oracle ACFS file system named .ACFS. (Note that hidden files and directories in Linux start with leading period.)

[oracle@racnode1 ~]$ ls -lFA /documents3
total 2851148
drwxr-xr-x 5 root   root           4096 Nov 26 17:57 .ACFS/
-rw-r--r-- 1 oracle oinstall 1239269270 Nov 27 16:02 linux.x64_11gR2_database_1of2.zip
-rw-r--r-- 1 oracle oinstall 1111416131 Nov 27 16:03 linux.x64_11gR2_database_2of2.zip
-rw-r--r-- 1 oracle oinstall  555366950 Nov 27 16:03 linux.x64_11gR2_examples.zip
drwx------ 2 root   root          65536 Nov 26 17:57 lost+found/

If you don't have the ORACLE_HOME environment variable set to the Oracle grid infrastructure home as explained in the prerequisites section to this guide, the mount command will fail as shown above. In order to mount the new cluster file system, the Oracle ASM ACFS binaries need access to certain shared libraries in the ORACLE_HOME for grid infrastructure. An easy workaround to get past this error is to set the ORACLE_HOME environment variable for grid infrastructure in the file /sbin/mount.acfs on all Oracle RAC nodes. The ORACLE_HOME should be set at the beginning of the file after the header comments as follows:

Found in the .ACFS are two directories named repl and snaps. All Oracle ACFS snapshots are stored in the snaps directory.

[oracle@racnode1 ~]$ ls -lFA /documents3/.ACFS
total 12
drwx------ 2 root root 4096 Nov 26 17:57 .fileid/
drwx------ 6 root root 4096 Nov 26 17:57 repl/
drwxr-xr-x 2 root root 4096 Nov 27 15:53 snaps/
Since no Oracle ACFS snapshots exist, the snaps directory is empty. 

[oracle@racnode1 ~]$ ls -lFA /documents3/.ACFS/snaps
total 0


Create Oracle ACFS Snapshot

Let's start by creating an Oracle ACFS snapshot named snap1 for the Oracle ACFS mounted on /documents3. This operation should be performed as root or the Oracle grid infrastructure owner:

[root@racnode1 ~]# /sbin/acfsutil snap create snap1 /documents3
acfsutil snap create: Snapshot operation is complete.

The data for the new snap1 snapshot will be stored in /documents3/.ACFS/snaps/snap1. Once the snapshot is created, any existing files and/or directories in the file system are automatically accessible from the snapshot directory. For example, when I created the snap1 snapshot, the three Oracle ZIP files were made available from the snapshot /documents3/.ACFS/snaps/snap1:

[oracle@racnode1 ~]$ ls -lFA /documents3/.ACFS/snaps/snap1
total 2851084
drwxr-xr-x 5 root   root           4096 Nov 26 17:57 .ACFS/
-rw-r--r-- 1 oracle oinstall 1239269270 Nov 27 16:02 linux.x64_11gR2_database_1of2.zip
-rw-r--r-- 1 oracle oinstall 1111416131 Nov 27 16:03 linux.x64_11gR2_database_2of2.zip
-rw-r--r-- 1 oracle oinstall  555366950 Nov 27 16:03 linux.x64_11gR2_examples.zip
?--------- ? ?      ?                 ?            ? lost+found 

It is important to note that when the snapshot gets created, nothing is actually stored in the snapshot directory, so there is no additional space consumption. The snapshot directory will only contain modified file blocks when a file is updated or deleted.

Restore Files From an Oracle ACFS Snapshot

When a file is deleted (or modified), this triggers an automatic backup of all modified file blocks to the snapshot. For example, if I delete the file /documents3/linux.x64_11gR2_examples.zip, the previous images of the file blocks are copied to the snap1 snapshot where it can be restored from at a later time if necessary:

[oracle@racnode1 ~]$ rm /documents3/linux.x64_11gR2_examples.zip

If you were looking for functionality in Oracle ACFS to perform a rollback of the current file system to a snapshot, then I have bad news; one doesn't exist. Hopefully this will be a feature introduced in future versions!

In the case where you accidentally deleted a file from the current file system, it can be restored by copying it from the snapshot, back to the the current file system:

[oracle@racnode1 ~]$ cp /documents3/.ACFS/snaps/snap1/linux.x64_11gR2_examples.zip /documents3

Display Oracle ACFS Snapshot Information

The '/sbin/acfsutil info fs' command can provide file system information as well as limited information on any Oracle ACFS snapshots:

[oracle@racnode1 ~]$ /sbin/acfsutil info fs /documents3
/documents3
    ACFS Version: 11.2.0.1.0.0
    flags:        MountPoint,Available
    mount time:   Sat Nov 27 03:07:50 2010
    volumes:      1
    total size:   26843545600
    total free:   23191826432
    primary volume: /dev/asm/docsvol3-300
        label:                 DOCSVOL3
        flags:                 Primary,Available
        on-disk version:       39.0
        allocation unit:       4096
        major, minor:          252, 153603
        size:                  26843545600
        free:                  23191826432
    number of snapshots:  1
    snapshot space usage: 560463872

From the example above, you can see that I have only one active snapshot that is consuming approximately 560MB of disk space. This coincides with the size of the file I removed earlier (/documents3/linux.x64_11gR2_examples.zip) which triggered a back up of all modified file image blocks.

To query all snapshots, simply list the directories under '<ACFS_MOUNT_POINT>/.ACFS/snaps'. Each directory under the snaps directory is an Oracle ACFS snapshot.

Another useful technique used to obtain information about Oracle ACFS snapshots is to query the view V$ASM_ACFSSNAPSHOTS from the Oracle ASM instance:

column snap_name    format a15  heading "Snapshot Name"
column fs_name      format a15  heading "File System"
column vol_device   format a25  heading "Volume Device"
column create_time  format a20  heading "Create Time"

======================================================================

SQL> select snap_name, fs_name, vol_device,
  2  to_char(create_time, 'DD-MON-YYYY HH24:MI:SS') as create_time
  3  from v$asm_acfssnapshots
  4  order by snap_name;

Snapshot Name   File System     Volume Device             Create Time
--------------- --------------- ------------------------- --------------------
snap1           /documents3     /dev/asm/docsvol3-300     27-NOV-2010 16:11:29

Delete Oracle ACFS Snapshot

Use the 'acfsutil snap delete' command to delete an existing Oracle ACFS snapshot:

[root@racnode1 ~]# /sbin/acfsutil snap delete snap1 /documents3
acfsutil snap delete: Snapshot operation is complete.


Managing ACFS

Oracle ACFS and Dismount or Shutdown Operations

If you take anything away from this article, know and understand the importance of dismounting any active file system configured with an Oracle ASM Dynamic Volume Manager (ADVM) volume device, BEFORE shutting down an Oracle ASM instance or dismounting a disk group! Failure to do so will result in I/O failures and very angry users!

After the file system(s) have been dismounted, all open references to Oracle ASM files are removed and associated disk groups can then be dismounted or the Oracle ASM instance shut down.

If the Oracle ASM instance or disk group is forcibly shut down or fails while an associated Oracle ACFS is active, the file system is placed into an offline error state. When the file system is placed in an offline error state, applications will start to encounter I/O failures and any Oracle ACFS user data and metadata being wrien at the time of the termination may not be flushed to ASM storage before it is fenced. If a SHUTDOWN ABORT operation on the Oracle ASM instance is required and you are not able to dismount the file system, issue two sync command to flush any cached file system data and metadata to persistent storage:

[root@racnode1 ~]# sync
[root@racnode1 ~]# sync

Using a two-node Oracle RAC, I forced an Oracle ASM instance shutdown on node 1 to simulate a failure: (Note: This should go without saying, but I'll say it anyway. DO NOT attempt the following on a production environment.)

SQL> shutdown abort
ASM instance shutdown

Any subsequent attempt to access an offline file system on that node will result in an I/O error:

[oracle@racnode1 ~]$ ls -l /documents3
ls: /documents3: Input/output error

[oracle@racnode1 ~]$ df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                     145344992  22459396 115383364  17% /
/dev/sdb1            151351424    192072 143346948   1% /local
/dev/sda1               101086     12632     83235  14% /boot
tmpfs                  2019256         0   2019256   0% /dev/shm
df: `/documents1': Input/output error
df: `/documents2': Input/output error
df: `/documents3': Input/output error
domo:PUBLIC          4799457152 1901758592 2897698560  40% /domo

Recovering a file system from an offline error state requires dismounting and remounting the Oracle ACFS file system. Dismounting an active file system, even one that is offline, requires stopping all applications using the file system, including any shell references. For example, I had a shell session that previously changed directory (cd) into the /documents3 file system before the forced shutdown:

[root@racnode1 ~]# umount /documents1
[root@racnode1 ~]# umount /documents2
[root@racnode1 ~]# umount /documents3
umount: /documents3: device is busy
umount: /documents3: device is busy

Use the Linux fuser or lsof command to identify processes and kill if necessary:

[root@racnode1 ~]# fuser /documents3
/documents3:         16263c

[root@racnode1 ~]# kill -9 16263

[root@racnode1 ~]# umount /documents3

Restart the Oracle ASM instance (or in my case, all Oracle grid infrastructure services were stopped as a result of me terminating the Oracle ASM instance):

[root@racnode1 ~]# /u01/app/11.2.0/grid/bin/crsctl stop cluster

[root@racnode1 ~]# /u01/app/11.2.0/grid/bin/crsctl start cluster

All of my Oracle ACFS volumes were added to the Oracle ACFS mount registry and will therefore automatically mount when Oracle grid infrastructure starts. If you need to manually mount the file system, verify the volume is enabled before attempting to mount:

[root@racnode1 ~]# mount
/dev/mapper/VolGroup00-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sdb1 on /local type ext3 (rw)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
oracleasmfs on /dev/oracleasm type oracleasmfs (rw)
domo:PUBLIC on /domo type nfs (rw,addr=192.168.1.121)
/dev/asm/docsvol1-300 on /documents1 type acfs (rw)
/dev/asm/docsvol2-300 on /documents2 type acfs (rw)
/dev/asm/docsvol3-300 on /documents3 type acfs (rw)

Resize File System

With Oracle ACFS, as long as there exists free space within the ASM disk group, any of the ASM volumes can be dynamically expanded which means the file system gets expanded as a result. Note that if you are using another file system other than Oracle ACFS, as long as that file system can support online resizing, they too can be dynamically re-sized. The one exception to 3rd party file systems is online shrinking. Ext3, for example, supports online resizing but does not support online shrinking.

Use the following syntax to add space to an Oracle ACFS on the fly without the need to take any type of outage.

First, verify there is enough space in the current Oracle ASM disk group to extend the volume:

SQL> select name, total_mb, free_mb, round((free_mb/total_mb)*100,2) pct_free
  2  from v$asm_diskgroup
  3  where total_mb != 0
  4  order by name;

Disk Group        Total (MB)    Free (MB)  % Free
--------------- ------------ ------------ -------
CRS                    2,205        1,809   82.04
DOCSDG1               98,303       12,187   12.40
FRA                   33,887       22,795   67.27
RACDB_DATA            33,887       30,584   90.25

The same task can be accomplished using the ASMCMD command-line utility:

[grid@racnode1 ~]$ asmcmd lsdg

From the 12GB of free space in the DOCSDG1 ASM disk group, let's extend the file system (volume) by another 5GB. Note that this can be performed while the file system is online and accessible by clients � no outage is required:

[root@racnode1 ~]# /sbin/acfsutil size +5G /documents3
acfsutil size: new file system size: 26843545600 (25600MB)

Verify the new size of the file system from all Oracle RAC nodes:

[root@racnode1 ~]# df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                     145344992  21952712 115890048  16% /
/dev/sdb1            151351424    192072 143346948   1% /local
/dev/sda1               101086     12632     83235  14% /boot
tmpfs                  2019256   1135852    883404  57% /dev/shm
domo:PUBLIC          4799457152 1901103872 2898353280  40% /domo
/dev/asm/docsvol1-300
                      33554432    197668  33356764   1% /documents1
/dev/asm/docsvol2-300
                      33554432    197668  33356764   1% /documents2
/dev/asm/docsvol3-300
                      26214400    183108  26031292   1% /documents3


[root@racnode2 ~]# df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                     145344992  13803084 124039676  11% /
/dev/sdb1            151351424    192072 143346948   1% /local
/dev/sda1               101086     12632     83235  14% /boot
tmpfs                  2019256   1135852    883404  57% /dev/shm
domo:Public          4799457152 1901103872 2898353280  40% /domo
/dev/asm/docsvol1-300
                      33554432    197668  33356764   1% /documents1
/dev/asm/docsvol2-300
                      33554432    197668  33356764   1% /documents2
/dev/asm/docsvol3-300
                      26214400    183108  26031292   1% /documents3

Useful ACFS Commands

This section contains several useful commands that can be used to administer Oracle ACFS. Note that many of the commands described in this section have already been discussed throughout this guide.

ASM Volume Driver

Load the Oracle ASM volume driver:

[root@racnode1 ~]# /u01/app/11.2.0/grid/bin/acfsload start -s

Unload the Oracle ASM volume driver:

[root@racnode1 ~]# /u01/app/11.2.0/grid/bin/acfsload stop

Check if Oracle ASM volume driver is loaded:

[root@racnode1 ~]# lsmod | grep oracle
oracleacfs            877320  4
oracleadvm            221760  8
oracleoks             276880  2 oracleacfs,oracleadvm
oracleasm              84136  1

ASM Volume Management

Create new Oracle ASM volume using ASMCMD

[grid@racnode1 ~]$ asmcmd volcreate -G docsdg1 -s 20G --redundancy unprotected docsvol3

Resize Oracle ACFS file system (add 5GB):

[root@racnode1 ~]# /sbin/acfsutil size +5G /documents3
acfsutil size: new file system size: 26843545600 (25600MB)

Delete Oracle ASM volume using ASMCMD:

[grid@racnode1 ~]$ asmcmd voldelete -G docsdg1 docsvol3

Disk Group / File System / Volume Information

Get detailed Oracle ASM disk group information:

[grid@racnode1 ~]$ asmcmd lsdg

Format an Oracle ASM cluster file system:

[grid@racnode1 ~]$ /sbin/mkfs -t acfs -b 4k /dev/asm/docsvol3-300 -n "DOCSVOL3"
mkfs.acfs: version                   = 11.2.0.1.0.0
mkfs.acfs: on-disk version           = 39.0
mkfs.acfs: volume                    = /dev/asm/docsvol3-300
mkfs.acfs: volume size               = 21474836480
mkfs.acfs: Format complete.

Get detailed file system information: :

[root@racnode1 ~]# /sbin/acfsutil info fs
/documents1
    ACFS Version: 11.2.0.1.0.0
    flags:        MountPoint,Available
    mount time:   Fri Nov 26 18:38:48 2010
    volumes:      1
    total size:   34359738368
    total free:   34157326336
    primary volume: /dev/asm/docsvol1-300
        label:
        flags:                 Primary,Available,ADVM
        on-disk version:       39.0
        allocation unit:       4096
        major, minor:          252, 153601
        size:                  34359738368
        free:                  34157326336
        ADVM diskgroup         DOCSDG1
        ADVM resize increment: 268435456
        ADVM redundancy:       unprotected
        ADVM stripe columns:   4
        ADVM stripe width:     131072
    number of snapshots:  0
    snapshot space usage: 0

/documents2
    ACFS Version: 11.2.0.1.0.0
    flags:        MountPoint,Available
    mount time:   Fri Nov 26 18:38:48 2010
    volumes:      1
    total size:   34359738368
    total free:   34157326336
    primary volume: /dev/asm/docsvol2-300
        label:
        flags:                 Primary,Available,ADVM
        on-disk version:       39.0
        allocation unit:       4096
        major, minor:          252, 153602
        size:                  34359738368
        free:                  34157326336
        ADVM diskgroup         DOCSDG1
        ADVM resize increment: 268435456
        ADVM redundancy:       unprotected
        ADVM stripe columns:   4
        ADVM stripe width:     131072
    number of snapshots:  0
    snapshot space usage: 0

Get ASM volume information:

[grid@racnode1 ~]$ asmcmd volinfo -a
Diskgroup Name: DOCSDG1

         Volume Name: DOCSVOL1
         Volume Device: /dev/asm/docsvol1-300
         State: ENABLED
         Size (MB): 32768
         Resize Unit (MB): 256
         Redundancy: UNPROT
         Stripe Columns: 4
         Stripe Width (K): 128
         Usage: ACFS
         Mountpath: /documents1

         Volume Name: DOCSVOL2
         Volume Device: /dev/asm/docsvol2-300
         State: ENABLED
         Size (MB): 32768
         Resize Unit (MB): 256
         Redundancy: UNPROT
         Stripe Columns: 4
         Stripe Width (K): 128
         Usage: ACFS
         Mountpath: /documents2

         Volume Name: DOCSVOL3
         Volume Device: /dev/asm/docsvol3-300
         State: ENABLED
         Size (MB): 25600
         Resize Unit (MB): 256
         Redundancy: UNPROT
         Stripe Columns: 4
         Stripe Width (K): 128
         Usage: ACFS
         Mountpath: /documents3

Get volume status using ASMCMD command:

[grid@racnode1 ~]$ asmcmd volstat

DISKGROUP NUMBER / NAME:  2 / DOCSDG1
---------------------------------------
  VOLUME_NAME
     READS           BYTES_READ      READ_TIME       READ_ERRS
     WRITES          BYTES_WRIEN   WRITE_TIME      WRITE_ERRS
  -------------------------------------------------------------
  DOCSVOL1
     517             408576          1618            0
     17007           69280768        63456           0
  DOCSVOL2
     512             406016          2547            0
     17007           69280768        66147           0
  DOCSVOL3
     13961           54525952        172007          0
     10956           54410240        41749           0

Enable a volume using the ASMCMD command:

[grid@racnode1 ~]$ asmcmd volenable -G docsdg1 docsvol3

Disable a volume using the ASMCMD command

[root@racnode1 ~]# umount /documents3
[root@racnode2 ~]# umount /documents3

[grid@racnode1 ~]$ asmcmd voldisable -G docsdg1 docsvol3

Mount Commands

Mount single Oracle ACFS volume on the local node:

[root@racnode1 ~]# /bin/mount -t acfs /dev/asm/docsvol3-300 /documents3

Unmount single Oracle ACFS volume on the local node:

[root@racnode1 ~]# umount /documents3

Mount all Oracle ACFS volumes on the local node using the metadata found in the Oracle ACFS mount registry:

[root@racnode1 ~]# /sbin/mount.acfs -o all

Unmount all Oracle ACFS volumes on the local node using the metadata found in the Oracle ACFS mount registry:

[root@racnode1 ~]# /bin/umount -t acfs -a

Oracle ACFS Mount Registry

Register new mount point in the Oracle ACFS mount registry:

[root@racnode1 ~]# /sbin/acfsutil registry -f -a /dev/asm/docsvol3-300 /documents3
acfsutil registry: mount point /documents3 successfully added to Oracle Registry

Query the Oracle ACFS mount registry:

[root@racnode1 ~]# /sbin/acfsutil registry
Mount Object:
  Device: /dev/asm/docsvol1-300
  Mount Point: /documents1
  Disk Group: DOCSDG1
  Volume: DOCSVOL1
  Options: none
  Nodes: all
Mount Object:
  Device: /dev/asm/docsvol2-300
  Mount Point: /documents2
  Disk Group: DOCSDG1
  Volume: DOCSVOL2
  Options: none
  Nodes: all
Mount Object:
  Device: /dev/asm/docsvol3-300
  Mount Point: /documents3
  Disk Group: DOCSDG1
  Volume: DOCSVOL3
  Options: none
  Nodes: all

Unregister volume and mount point from the Oracle ACFS mount registry: 

[root@racnode1 ~]# acfsutil registry -d /documents3
acfsutil registry: successfully removed ACFS mount point /documents3 from Oracle Registry

Oracle ACFS Snapshots

Use the 'acfsutil snap create' command to create an Oracle ACFS snapshot named snap1 for an Oracle ACFS mounted on /documents3: :

[root@racnode1 ~]# /sbin/acfsutil snap create snap1 /documents3
acfsutil snap create: Snapshot operation is complete.

Use the 'acfsutil snap delete' command to delete an existing Oracle ACFS snapshot:

[root@racnode1 ~]# /sbin/acfsutil snap delete snap1 /documents3
acfsutil snap delete: Snapshot operation is complete.

Oracle ASM / ACFS Dynamic Views

This section contains information about using dynamic views to display Oracle Automatic Storage Management (Oracle ASM), Oracle Automatic Storage Management Cluster File System (Oracle ACFS), and Oracle ASM Dynamic Volume Manager (Oracle ADVM) information. These views are accessible from the Oracle ASM instance.

Oracle Automatic Storage Management (Oracle ASM)
View Name Description
V$ASM_ALIAS Contains one row for every alias present in every disk group mounted by the Oracle ASM instance.
V$ASM_ATTRIBUTE Displays one row for each attribute defined. In addition to attributes specified by CREATE DISKGROUP and ALTER DISKGROUP statements, the view may show other attributes that are created automatically. Attributes are only displayed for disk groups where COMPATIBLE.ASM is set to 11.1 or higher.
V$ASM_CLIENT In an Oracle ASM instance, identifies databases using disk groups managed by the Oracle ASM instance.

In a DB instance, contains information about the Oracle ASM instance if the database has any open Oracle ASM files.

V$ASM_DISK Contains one row for every disk discovered by the Oracle ASM instance, including disks that are not part of any disk group.

This view performs disk discovery every time it is queried.

V$ASM_DISK_IOSTAT Displays information about disk I/O statistics for each Oracle ASM client.

In a DB instance, only the rows for that instance are shown.

V$ASM_DISK_STAT Contains the same columns as V$ASM_DISK, but to reduce overhead, does not perform a discovery when it is queried. It only returns information about any disks that are part of mounted disk groups in the storage system. To see all disks, use V$ASM_DISK instead.
V$ASM_DISKGROUP Describes a disk group (number, name, size related info, state, and redundancy type).

This view performs disk discovery every time it is queried.

V$ASM_DISKGROUP_STAT Contains the same columns as V$ASM_DISKGROUP, but to reduce overhead, does not perform a discovery when it is queried. It does not return information about any disks that are part of mounted disk groups in the storage system. To see all disks, use V$ASM_DISKGROUP instead.
V$ASM_FILE Contains one row for every Oracle ASM file in every disk group mounted by the Oracle ASM instance.
V$ASM_OPERATION In an Oracle ASM instance, contains one row for every active Oracle ASM long running operation executing in the Oracle ASM instance.

In a DB instance, contains no rows.

V$ASM_TEMPLATE Contains one row for every template present in every disk group mounted by the Oracle ASM instance.
V$ASM_USER Contains the effective operating system user names of connected database instances and names of file owners.
V$ASM_USERGROUP Contains the creator for each Oracle ASM File Access Control group.
V$ASM_USERGROUP_MEMBER Contains the members for each Oracle ASM File Access Control group.

 

Oracle Automatic Storage Management Cluster File System (Oracle ACFS)
View Name Description
V$ASM_ACFSSNAPSHOTS Contains snapshot information for every mounted Oracle ACFS file system.
V$ASM_ACFSVOLUMES Contains information about mounted Oracle ACFS volumes, correlated with V$ASM_FILESYSTEM.
V$ASM_FILESYSTEM Contains columns that display information for every mounted Oracle ACFS file system.
V$ASM_VOLUME Contains information about each Oracle ADVM volume that is a member of an Oracle ASM instance.
V$ASM_VOLUME_STAT Contains information about statistics for each Oracle ADVM volume.

Use fsck to Check and Repair the Cluster File System

Use the regular Linux fsck command to check and repair the Oracle ACFS. This only needs to be performed from one of the Oracle RAC nodes:

[root@racnode1 ~]# /sbin/fsck -t acfs /dev/asm/docsvol3-300
fsck 1.39 (29-May-2006)
fsck.acfs: version                   = 11.2.0.1.0.0
fsck.acfs: ACFS-00511: /dev/asm/docsvol3-300 is mounted on at least one node of the cluster.
fsck.acfs: ACFS-07656: Unable to continue

The fsck operating cannot be performed while the file system is online. Unmount the cluster file system from all Oracle RAC nodes:

[root@racnode1 ~]# umount /documents3

[root@racnode2 ~]# umount /documents3

Now check the cluster file system with the file system unmounted:

[root@racnode1 ~]# /sbin/fsck -t acfs /dev/asm/docsvol3-300
fsck 1.39 (29-May-2006)
fsck.acfs: version                   = 11.2.0.1.0.0
Oracle ASM Cluster File System (ACFS) On-Disk Structure Version: 39.0
*****************************
********** Pass 1: **********
*****************************
The ACFS volume was created at  Fri Nov 26 17:20:27 2010
Checking primary file system...

                Files checked in primary file system: 100%



        Checking if any files are orphaned...


        0 orphans found

fsck.acfs: Checker completed with no errors.

Remount the cluster file system on all Oracle RAC nodes:

[root@racnode1 ~]# /bin/mount -t acfs /dev/asm/docsvol3-300 /documents3

[root@racnode2 ~]# /bin/mount -t acfs /dev/asm/docsvol3-300 /documents3

Drop ACFS / ASM Volume

Unmount the cluster file system from all Oracle RAC nodes:

[root@racnode1 ~]# umount /documents3

[root@racnode2 ~]# umount /documents3

Log in to the ASM instance and drop the ASM dynamic volume from one of the Oracle RAC nodes:

[grid@racnode1 ~]$ sqlplus / as sysasm

SQL> ALTER DISKGROUP docsdg1 DROP VOLUME docsvol3;

Diskgroup altered.

The same task can be accomplished using the ASMCMD command-line utility:

[grid@racnode1 ~]$ asmcmd voldelete -G docsdg1 docsvol3

Unregister the volume and mount point from the Oracle ACFS mount registry from one of the Oracle RAC nodes:

[root@racnode1 ~]# acfsutil registry -d /documents3
acfsutil registry: successfully removed ACFS mount point /documents3 from Oracle Registry

Finally, remove the mount point directory from all Oracle RAC nodes (if necessary):

[root@racnode1 ~]# rmdir /documents3

[root@racnode2 ~]# rmdir /documents3

 

 
 
 
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