Provided by Charles Kim, Oracle ACE Director
Oracle Database Experts
By Charles Kim
Rename Disk Group
As of Oracle Database 11g Release 2, we can now rename disk groups. Why is this important? There’s two great reason why I think this feature is really beneficial for lot of companies. First, companies who leverage hardware mirroring or triple mirroring technologies such as EMC Business Continuity Volumes (BCV) or Hitachi Shadow Image (SI) can really benefit from this. Companies can now break their BCV or SI and rename their disk group where they have their production database and mount it again as another diskgroup. This way they can stand up another copy of their production database on the same physical server with minimal effort.
Note:
1. As of the initial release of Oracle Database 11g Release 2, the disk group rename feature does not handle the remaining task of standing up another database. You still have to re-catalog all the database files with the renamed disk group name. Additionally, you will have to create a new DB ID (nid).
2. If your company happens to have standardized disk group names with easily identifiable names such as as DATA, FLASH, LOBDATA, or FRA, you may have the same disk group names in Production, Staging, DEV and even disaster recovery site. For example, you can zone your production BCV or SI disks to your staging/Pre-Production/Model servers, rename the disk group called DATA to STAGE_DATA, and stand up the database from your BCV/SI.
Likewise, if you built disk groups with intelligent naming schemes (being a forward thinking architect 
), you may now choose to create easily identifiable disk group names such as DATA, FLASH, FRA, LOBDATA, etc.
Let’s look at the process of renaming a disk group. In order to rename a disk group, the disk group must be disounted across all the RAC nodes:
ASMCMD> umount dg_external ASMCMD> umount fra
You can rename a disk group in one of two ways. The first option (default) renames the disk group in a single command. In our example, we will also specify the verbose mode for additional details in the output. The second option will create a configuration file at the end of phase one and will use the configuration file to complete the rename disk group operation.
Option #1 – Phase=Both:
The default phase is both.
[oracle@jin1 ~]$ renamedg dgname=fra newdgname=flash verbose=true
Parsing parameters..
Parameters in effect:
Old DG name : FRA
New DG name : FLASH
Phases :
Phase 1
Phase 2
Discovery str : (null)
Clean : TRUE
Raw only : TRUE
renamedg operation: dgname=fra newdgname=flash verbose=true
Executing phase 1
Discovering the group
Performing discovery with string:
Identified disk ASM:/opt/oracle/extapi/32/asm/orcl/1/libasm.so:ORCL:FRA1 with disk number:0 and timestamp (32924850 209876992)
Checking for hearbeat...
Re-discovering the group
Performing discovery with string:
Identified disk ASM:/opt/oracle/extapi/32/asm/orcl/1/libasm.so:ORCL:FRA1 with disk number:0 and timestamp (32924850 209876992)
Checking if the diskgroup is mounted
Checking disk number:0
Checking if diskgroup is used by CSS
Generating configuration file..
Completed phase 1
Executing phase 2
Looking for ORCL:FRA1
Modifying the header
Completed phase 2
Terminating kgfd context 0xb7f2c050
Let’s mount the renamed disk group:
[oracle@jin1 ~]$ asmcmd mount flash [oracle@jin1 ~]$ asmcmd lsdg State Type Rebal Sector Block AU Total_MB Free_MB Req_mir_free_MB Usable_file_MB Offline_disks Voting_files Name MOUNTED EXTERN N 512 4096 1048576 23460 13140 0 13140 0 N DATA/ MOUNTED EXTERN N 512 4096 1048576 42068 42016 0 42016 0 N FLASH/ MOUNTED EXTERN N 512 4096 1048576 45792 41631 0 41631 0 N LOBDATA/
Option #2 – Phase 1 followed by Phase 2:
This option basically involves two steps to renaming a disk group. The first step, referred to as phase one, generates a configuration file. The config file has line item entries for each disk with changes to be made. The second step called phase two uses the generated config file to perform the rename function.
Another important information to note is that the renamedg command is an OS utility (not an asmcmd command). if you type renamedg with the -help option, you can get the complete syntax:
[oracle@jin1 ~]$ renamedg -help
Parsing parameters..
phase Phase to execute,
(phase=ONE|TWO|BOTH), default BOTH
dgname Diskgroup to be renamed
newdgname New name for the diskgroup
config intermediate config file
check just check-do not perform actual operation,
(check=TRUE/FALSE), default FALSE
confirm confirm before committing changes to disks,
(confirm=TRUE/FALSE), default FALSE
clean ignore errors,
(clean=TRUE/FALSE), default TRUE
asm_diskstring ASM Diskstring (asm_diskstring='discoverystring',
'discoverystring1' ...)
verbose verbose execution,
(verbose=TRUE|FALSE), default FALSE
keep_voting_files Voting file attribute,
(keep_voting_files=TRUE|FALSE), default FALSE
Let’s start the process, phase one, by creating our configuration file:
[oracle@jin1 ~]$ renamedg -phase one -dgname dg_external -newdgname lobdata -config rename_dg_external_2.conf Parsing parameters.. renamedg operation: -phase one -dgname dg_external -newdgname lobdata -config rename_dg_external_2.conf Executing phase 1 Discovering the group Checking for hearbeat... Re-discovering the group Generating configuration file.. Completed phase 1
The configuration file rename_dg_external_2.conf looks like this:
[oracle@jin1 ~]$ cat rename_dg_external_2.conf ORCL:HIGH1 DG_EXTERNAL LOBDATA ORCL:HIGH2 DG_EXTERNAL LOBDATA ORCL:HIGH3 DG_EXTERNAL LOBDATA
Now, let’s apply the configuration file and rename our diskgroup from DG_EXTERNAL to LOBDATA:
[oracle@jin1 ~]$ renamedg -phase two -dgname dg_external -newdgname lobdata -config rename_dg_external_2.conf Parsing parameters.. renamedg operation: -phase two -dgname dg_external -newdgname lobdata -config rename_dg_external_2.conf Executing phase 2 Completed phase 2
We should now be able to mount the renamed LOBDATA disk group with asmcmd:
[oracle@jin1 ~]$ asmcmd ASMCMD> mount lobdata
With the lsdg asmcmd command, you can verify that the LOBDATA disk group is truly mounted:
ASMCMD> lsdg State Type Rebal Sector Block AU Total_MB Free_MB Req_mir_free_MB Usable_file_MB Offline_disks Voting_files Name MOUNTED EXTERN N 512 4096 1048576 15640 5332 0 5332 0 N DATA/ MOUNTED EXTERN N 512 4096 1048576 45792 45736 0 45736 0 N LOBDATA/
Posted by Charles Kim, Oracle ACE
New ways to create disk groups in Oracle Database 11g Release 2
Guess what? As of Oracle Database 11g Release 2, we can create disk groups using the asmcmd command. Check out one of the new ways we can create a diskgroup using an XML file as a template. The mkdg ASMCMD command can accept an xml file as a parameter to create a disk group:
[oracle@jin1 ~]$ asmcmd mkdg dg_high.xml
[oracle@jin1 ~]$ cat dg_high.xml
<dg name="dg_high" redundancy="high">
<fg name="fg1">
<dsk string="ORCL:HIGH1" />
</fg>
<fg name="fg2">
<dsk string="ORCL:HIGH2" />
</fg>
<fg name="fg3">
<dsk string="ORCL:HIGH3" />
</fg>
<a name="compatible.asm" value="11.2"/>
<a name="compatible.rdbms" value="11.2"/>
</dg>
And if we refresh our Automatic Storage Management main screen, we see the new diskgroup as shown here:
Let’s drop the dg_high disk group and show you how you can do this same thing with asmca command line interface.
Here’s the super hard syntax to drop the dg_high disk group:
ASMCMD> dropdg dg_high
Now, let’s create the disk group with asmca command line interface:
[oracle@jin1 ~]$ ksh cr_dg_high.txt DiskGroup dg_high created successfully. [oracle@jin1 ~]$ cat cr_dg_high.txt asmca -silent -createDiskGroup \ -diskgroupname dg_high \ -redundancy high \ -disk 'ORCL:HIGH1' -disk 'ORCL:HIGH2' -disk 'ORCL:HIGH3' \ -failuregroup fg1 \ -failuregroup fg2 \ -failuregroup fg3 \ -au_size 64 \ -compatible.asm '11.2.0.0.0' \ -compatible.rdbms '11.2.0.0.0' \ -compatible.advm '11.2.0.0.0'
In the example with the asmca command line syntax, we added a little twist by adding the allocation extent to 64 MB and adding the compatible.advm attribute.
Majority of the ASM customers run external redundancy and have the protection provided to us by the storage array vendors. Let’s see our same example and show how to create an external redundant diskgroup. Here’s the XML file for the external redundancy disk group:
[oracle@jin1 ~]$ cat dg_external.xml
<dg name="dg_external" redundancy="external">
<dsk string="ORCL:HIGH1" />
<dsk string="ORCL:HIGH2" />
<dsk string="ORCL:HIGH3" />
<a name="compatible.asm" value="11.2"/>
<a name="compatible.rdbms" value="11.2"/>
<a name="compatible.advm" value="11.2"/>
</dg>
Using asmcmd, we will create the dg_external diskgroup:
[oracle@jin1 ~]$ asmcmd mkdg dg_external.xml
Alternatively, you can create the diskgroup in a single inline command as shown here:
ASMCMD> mkdg '<dg name="dg_external" redundancy="external"> <dsk string="ORCL:HIGH1" /> <dsk string="ORCL:HIGH2" /> <dsk string="ORCL:HIGH3" /> <a name="compatible.asm" value="11.2"/> <a name="compatible.rdbms" value="11.2"/> <a name="compatible.advm" value="11.2"/> </dg>'
Obviously, nobody in their right mind would create a disk in this format. Wether you use asmca or asmcmd with an XML file or even the dreaded SQL*Plus, figure out what works best for you and stick with it. Depending on if you are a Unix System Administrator or Database Administrator, you may choose a different tool as your standard.
Posted by Charles Kim
Maintaining ASM Volumes and Cluster File Systems in Oracle Database 11g Release 2
From the ASM Cluster File System main screen (Click on the ASM Cluster File System Tab), we will click on the VOL_LOGFILE volume URL to see volume related information:
Click on the Edit button to edit the current volume:
From the Edit Volume screen, click on the URL next to the Size Field. You will be redirected to the Resize ASM Cluster File System screen:
Let’s change the size from 2 GB to 3GB and click on the show command to see what commands EM will submit do to resize the file system:
Show Command /sbin/acfsutil size 3G /apps/oracle/acfsmounts/data_vol_logfile
The acfsutil above will resize the file system and resize the volume at the same time.
Click on Return to go back to the Resize ASM Cluster File System screen
Click on the OK button
Again, you will be prompted to provide ASM Cluster File System Host Credentials if you have not saved your credentials as a preferred credential yet.
Enter your username credentials and click on Continue
When the task is complete, you will be routed to the ASM Cluster File System: /apps/oracle/acfsmounts/data_vol_logfile screen
(You may see a screen stating that the no monitoring data has been collected for this ASM Cluster File system.)
Click on the ASM Cluster File System breadcrumb URL
In the ASM Cluster File System main screen, you will see the changed size for the /apps/oracle/acfsmounts/data_vol_logfile file system.
From the ASM Cluster File System main screen, you will see buttons to Delete the mount point, to view the contents of the file system, register/deregister a file system, mount all and dismount all file systems. You will also notice that the actions drop list has the functions to resize an existing file system and to check and repair a file system. In order to perform a check and repair function, the file system must be dismounted.
Let’s go an dismount a file system:
Click on the radio button of the file system that you want to dismount
You will see the Dismount ASM Cluster File System screen. As you can guess, Enterprise Manager only generates the syntax that need to be executed by someone with root privileges (or sudo). Click on the Return button to go back to the ASM Cluster File System main page.
Posted by Charles Kim, Oracle ACE
Creating ASM Volumes and Cluster File Systems with Enterprise Mangers in 11g Release 2
Let’s login to the EM Database Control. Your URL to login should be something like this:
https://jin1:1158/em
Scroll to the bottom of the screen to the instances section. You will see the database and ASM instance information as shown here:
Click on the +ASM1_[HOSTNAME] instance URL
The Automatic Storage Management Home page now includes sections for ASM Clustered File Systems (ACFS) and Volumes.
You will also notice a new tab dedicated to support the new ASM Cluster File System feature. The ASM Cluster File System tab will simplify your ability to create volumes, create cluster file systems and ACFS snapshots. In this blog post, we will only cover creating volumes and ASM cluster file systems.
Oracle ASM Dynamic Volume Manager (Oracle ADVM)
The new Oracle ASM Dynamic Volume Manager (Oracle ADVM) provides volume management services and a standard disk device driver interface. A volume device is constructed from an ASM volume. You can create one or more volumes devices within a disk group. Once you create a volume, you can create a file system using that volume. You can create an ASM cluster file system off of the ASM volume. Likewise, you can create an EXT3 or OCFS2 file system based on the ASM volume. Likewise, as Oracle ports ACFS to other Unix Platforms, you can create the OS native file systems using Oracle ASM disk group volumes. Oracle ACFS is layered on ASM through the ADVM interface.
Note:
Creating an OCFS2 file system on top of ASM Disk Group does not make sense, but it is do-able.
Requirements for ADVM
1. COMPATIBLE.ASM and COMPATIBLE.ADVM attributes must be set to 11.2.
2. Volume name can be a maximum of 11 alphanumeric characters (no dashes and first character must be alphabetic)
Let’s click on the new ASM Cluster File System tab and create ourselves an ASM Cluster File System.
You will see the following screen:
Notice that we already created the VOL_RPTS volume that is already mounted as /apps/oracle/acfsmounts/data_vol_rpts mount point. Let’s create a new volume and mount another file system. To start this process, click on the Create button on the right corner. You will be directed to the Create ASM Cluster File System screen. Before we can create an ASM Cluster File System, we must first create a volume. Click on the the Create ASM Volume button. From the Create ASM Volume screen,
Enter the values for Volume, Data Group, and Size.
Notice the size can be specified in MB, GB and TB.
If you want to see the SQL, click on the Show Command button
Click on the Return button to go back to the Create ASM Cluster File System Screen
You will notice that the Volume Device field is populated with the new Volume that you just created
Specify a label (optional) if you want and specify a Mount Point
Again, click on the Show Command button
Click on the Return button to back to the Create ASM Cluster File System screen
Click on the OK button to create the ACFS file system
You will be requested to enter OS credentials – This operating system user name and password will be used to perform ASM Cluster File System operations on this host.
You will receive a confirmation status on top of the screen indicating that the file system was successfully created:
Next, click on the VOL_LOGFILE Volume radio button and click on the Mount button on the top left portion of the screen. You will be routed to the Mount ASM Cluster File System: [VOLUME_NAME] screen.
Unfortunately, you will not be able to mount the file system from Enterprise Manager. Only thing you will be able to do is generate the command and ask your system administrator to mount the file system.
As the root user, issue the mount command shown from this screen.
[root@jin1 oracle]# /bin/mount -t acfs /dev/asm/vol_logfile-340 /apps/oracle/acfsmounts/data_vol_logfile
Now from the OS, you can see the output from the df -h command to see the new file system mounted:
[root@jin1 oracle]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
122G 11G 106G 9% /
/dev/sda1 99M 12M 82M 13% /boot
tmpfs 1.1G 154M 874M 15% /dev/shm
.host:/ 163G 141G 23G 87% /mnt/hgfs
/dev/asm/vol_rpts-340
5.0G 49M 5.0G 1% /apps/oracle/acfsmounts/data_vol_rpts
/dev/asm/vol_logfile-340
2.0G 41M 2.0G 2% /apps/oracle/acfsmounts/data_vol_logfile
Click on the Return button to go back to the Mount Cluster File System screen. Click the Return button again to back to the ASM Cluster File System main screen.
Posted by Charles Kim, Oracle ACE
Creating ASM Snapshots with Enterprise Mangers in 11g Release 2
Earlier we went through the exercise to create ASM Volumes and Cluster File Systems within ASM disk groups. Another great feature introduced in Oracle Database 11g Release 2 is the capability to create snapshot images of the ASM cluster file systems. Oracle allows up to 63 read-only snapshots of their file system leveraging the Copy-on-write (COW) technology. When a snapshot request is submitted, COW technology stores only the meta-data about where the original data is stored is copied. The creation of the snapshot should be almost instantaneous since only the meta-data is being copied. The snapshot copy then tracks changed blocks to a snapshot storage location as writes are being performed. The original data that is being written to is copied into the designated area on the file system before the original data is overwritten. This is where the name copy-on-write comes from.
Read requests for unchanged data blocks go directly to the original file system. Read requests for changed data blocks are directed to the copied block on the snapshot storage volume. Please remember that the original data is only copied once. Subsequence change to the same block is not copied more than once.
EM provides full support for ASM snapshots. Let’s go EM Database Control and see how this is done. From the ASM Cluster File System tab, select a mount point and click on the Create Snapshot button.
You should se the Create Snapshot on ASM Cluster File System screen. Notice that the Snapshot Name column is auto-populated for you with shapshot_[date]_[time] format. You can change this to any kind of standard you may designate for your company.
Notice the Delete the oldest snapshot (62 remaining before the maximum limit is reached) check box. You will see this check box as you create your second and subsequent ASM snapshots. You will also see the oldest snapshot with the URL for easy convenience.
Click on the Show Command button to see the command line syntax that EM is about to submit:
For the command line DBAs, we can create snapshots copying and pasting from the following syntax:
/sbin/acfsutil snap create "snapshot_20090911_104833" /apps/oracle/acfsmounts/data_vol_logfile
Click on the Return button
From the Create Snapshot on ASM Cluster File System screen, click on the OK button. You will be routed to the ASM Cluster File System Host Credentials screen. Enter the username and password for oracle. If you want EM Database Control to remember the username and password, you can click on the option to save as preferred credential checkbox.
Click on the Continue button
You will be redirected to the ASM Cluster File System main page and will see a successful confirmation status:
We created our snapshot of the /apps/oracle/acfsmounts/data_vol_logfile file system. From the ASM Cluster File System main screen, click on the file system URL and look at some General information about that mount point.
You can see the general usage information and alerts for the file system. Usage information of the file system include Size (GB), Used (GB), Free (GB), Used (%), Allocated Space (GB) and Space Used by Snapshots (MB) or (GB).
Also in this screen, you will notice the Snapshots tab. Click on the Snapshots tab to see all the snapshot history for this ACFS file system. You can create additional snapshots or even delete existing snapshots from this screen:
And, of course, you can search for a specific snapshot using the search option on the snapshot name.
Posted by Charles Kim, Oracle ACE