OCR stored in two disk groups

Grid Version: 11.2.0.3
RHEL 5.8
When I run ocrcheck in our 11.2 cluster, I see the OCR being stored in two diskgroups, DATA and FRA ? Is this Ok ?
ocrcheck output shown below
$ ocrcheck
Status of Oracle Cluster Registry is as follows :
         Version                  :          3
         Total space (kbytes)     :     262120
         Used space (kbytes)      :       6620
         Available space (kbytes) :     255500
         ID                       : 1164495503
         Device/File Name         :      +DATA
                                    Device/File integrity check succeeded
         Device/File Name         :       +FRA
                                    Device/File integrity check succeeded
                                    Device/File not configured
                                    Device/File not configured
                                    Device/File not configured
         Cluster registry integrity check succeeded
         Logical corruption check bypassed due to non-privileged userIn my old shop , we used to create a dedicated disk group (+DG_OCR_VOTE) to store OCR, Voting disk and SPFILE.

In your case 2 disk group is configured for OCR. There have free 3 disk group , too.
$ ocrcheck
Status of Oracle Cluster Registry is as follows :
Version                  :          3
Total space (kbytes)     :     262120
Used space (kbytes)      :       6620
Available space (kbytes) :     255500
ID                       : 1164495503
Device/File Name         :      +DATA                                   -- 1
Device/File integrity check succeeded
Device/File Name         :       +FRA                                    -- 2
Device/File integrity check succeeded
Device/File not configured                     -- 3
Device/File not configured                     -- 4
Device/File not configured                     -- 5
Cluster registry integrity check succeededThanks
Mahir M. Quluzade

Similar Messages

How do I define 2 disk groups for ocr and voting disks at the oracle grid infrastructure installation window

Hello,
It may sound too easy to someone but I need to ask it anyway.
I am in the middle of building Oracle RAC 11.2.0.3 on Linux. I have 2 storage and I created three LUNs in each of storage so 6 LUNs in total look in both of servers. If I choose NORMAL as a redundancy level, is it right to choose my 6 disks those are created for OCR_VOTE at the grid installation? Or should I choose only 3 of them and configure mirroring at latter stage?
The reason why I am asking this is that I didn't find any place to create asm disk group for ocr and voting disks at the oracle grid infrastructure installation window. In fact, I would to like to create two disk groups in which one of groups contains three disks those were brought from storage 1 and the second one contains rest three 3 disk that come from the last storage.
I believe that you will understand the manner and help me on choosing proper way.
Thank you.

Hi,
You have 2 Storage H/W.
You will need to configure a Quorum ASMDisk to store a Voting Disk.
Because if you lose 1/2 or more of all of your voting disks, then nodes get evicted from the cluster, or nodes kick themselves out of the cluster.
You must have the odd number of voting disk (i.e 1,3 or 5) one voting disk per ASM DISK, So 1 Storage will hold more voting disk than another storage.
(e.g 3 Voting Disk - 2 voting stored in stg-A and 1 voting disk store in stg-B)
If fail the storage that hold the major number of Voting disk the whole cluster (all nodes) goes down. Does not matter if you have a other storage online.
It will happen:
https://forums.oracle.com/message/9681811#9681811
You must configure your Clusterware same as RAC extended
Check this link:
http://www.oracle.com/technetwork/database/clusterware/overview/grid-infra-thirdvoteonnfs-131158.pdf
Explaining: How to store OCR, Voting disks and ASM SPFILE on ASM Diskgroup (RAC or RAC Extended) | Levi Pereira | Oracl…

Multiple disk group pros/cons

hello all,
This is with regards to 11.2.0.3 DB(RAC) on RHEL 6
i am trying to identify the pro's/con's of using multiple ASM Diskgroup. I understand oracle recommends/best practice is to have 2 DG (one data and one flash) and you can place multiple copies of control files/online redo logs(and thats the way i want to go). But would that same be true if i use different set of DISK. For example we have multiple RAID 10 devices and multiple of SSD devices for us that we can use for this ASM instance. And i was thinking to create 2 more Disk group (call it DG_SYS1 and DG_SYS2) and use that to put my online redo logs, control file and temp and system table space there.
i understand in a standalone system(where regular file system is being used), they(online redo/control file) are usually on there own drives, but with ASM when i am already using external RAID 10 config + ASM striping i assume the IO would faster or am i better of using the SSD that i can have for my redo/control? What would be the pro's/cons of it (besides managing multiple DG)..

Reason that Oracle suggests to have two disk groups is because the very idea of ASM is the storage consolidation and to take the best advantage of that storage for all the databases. But having two dg's is not a norm. If you have different kinds of databases, if you have different capacity disks, you probably should have more dg's. Also, I am not sure why you are using RAID 0 along with ASM striping?
user13454469 wrote:
hello all,
This is with regards to 11.2.0.3 DB(RAC) on RHEL 6
i am trying to identify the pro's/con's of using multiple ASM Diskgroup. I understand oracle recommends/best practice is to have 2 DG (one data and one flash) and you can place multiple copies of control files/online redo logs(and thats the way i want to go). But would that same be true if i use different set of DISK. For example we have multiple RAID 10 devices and multiple of SSD devices for us that we can use for this ASM instance. And i was thinking to create 2 more Disk group (call it DG_SYS1 and DG_SYS2) and use that to put my online redo logs, control file and temp and system table space there.
i understand in a standalone system(where regular file system is being used), they(online redo/control file) are usually on there own drives, but with ASM when i am already using external RAID 10 config + ASM striping i assume the IO would faster or am i better of using the SSD that i can have for my redo/control? What would be the pro's/cons of it (besides managing multiple DG)..
Aman....

Standby Database ASM Disk Groups

Hi Guys
I wonder if anyone can tell me - does a standby database have to have an identical configuration for its ASM Disk Groups?
My production database has two disk groups, one for data and the other for temp. Can I get away with a single diskgroup in my standby database or would I need two of the same name as the production database?
Cheers
Simon

Hi Saml
I have been busy googling at the same time as discussing this and it would appear that it will use the db_file_name_convert:
http://asanga-pradeep.blogspot.com.au/2012/07/11gr2-standalone-data-guard-with-asm.html
The link above shows the output of someones RMAN session where the OMF names are changed automatically. Problem is that some people are recommending that the parameter not be used, so now I am really confused!
I think I will try the parameter, if it doesnt work or the duplicate fails I will drop the temp table space in production and then do the duplicate, then recreate the temp tablespace. I can do that because there will be no one on the system on Sunday when I do it.
Thanks again for your help - I will let you know how it goes.
Ragards
Simon

How to add ASM Disk to Disk Group that is shown as MEMBER?

HI,
We have a Production Oracle RAC on HP-UX. We have Two Disk Groups one for Arcive (ARC_DISK) and other for Database(DATA_DISK).
Today I wanted to add another 200 GB of Disk Space to the DATA_DISK Group.
I opened DBCA and could not find the new disk in the 'Show Candidates' option. But after the Unix admin changed the ownership and permission of the Disk, it was shown in 'Show Candidates' option. I selected this Disk and continued but got an error later as we didnt change the ownership and permission from the 2nd Unix server. After doing this, , when I open DBCA to add disk, nothing is shown in 'Show Candidates' option but when we click on 'Show All', the new disk is listed as MEMBER (header status) but not allocated to any Disk Group.
I would like to know how to allocate this Disk (which is already shown as MEMBER) to the DATA_DISK - ASM diskgroup. This is a production database system.
Rgds,
Thiru

user1983888 wrote:
Hi,
Due to huge difference in Disk Size which I am trying to add to the existing Disk Group which has 1024 GB of Disk, would it be a better idea to create a new Disk Group with 200g GB Disk? Will this command work as the header_status is already MEMBER?
SQL>CREATE DISKGROUP DATA_DISK1
EXTERNAL REDUNDANCY
DISK 'disk path';
Thanks.Yes, you can create new diskgroup (DATA_DISK1). Just make sure all datafile in DATA_DISK autoextend off, then create all your new datafile to the new diskgroup DATA_DISK1. The command will not work as the header_status is MEMBER. You'll receive ORA-15018 & ORA-15033 error. As I mentioned before, you need to use FORCE option or format the disk using dd* command before perform above command.
1st Option : (Format the raw disk using dd command creating new diskgroup. Header_status MEMBER -> CANDIDATE). E.g.
1. dd if=/dev/zero of=/dev/rdsk/c2t1d0 bs=8192 count=1000 //any rac nodes
2. # chown oracle:oinstall /dev/rdsk/c2t1d0 //perform on both node. This apply if using LVM or direct access to raw
3. SQL> create diskgroup data_disk1 external redundancy disk '/dev/rdsk/c2t1d0'; //any RAC node in ASM instance
4. SQL> alter diskgroup data_disk1 mount; //try to mount on the other node
2nd Option : (Using FORCE option when creating the new diskgroup. Header_Status = MEMBER)
1. # chown oracle:oinstall /dev/rdsk/c2t1d0 //perform on both node. This apply if using LVM or direct access to raw
2. SQL> create diskgroup data_disk1 external redundancy disk '/dev/rdsk/c2t1d0' force; //any RAC node in ASM instance
3. SQL> alter diskgroup data_disk1 mount; //try to mount on the other node
Just be careful when using FORCE option or DD command. If you perform this operation on existing ASM disk groups disk, it may destroy existing disk groups.

Recover OCR and VOTE disk after complete corruption of ASM disk groups.

Hi Gurus,
I am simulating a recovery situation to perform recover of OCR and Vote files after complete corruption of ASM related disks and diskgroups. I have setup my environment as follows:\
Environment: RAC
OS: OEL 5.5 32-bit
GI Version: 11.2.0.2.0
ASM Disk groups: +OCR, +DATA
OCR, Vote Files location: +OCR
ASM Redundancy: External
ASM Disks: /dev/asm-disk1, /dev/asm-disk2
/dev/asm-disk1 - mapped on +OCR
/dev/asm-disk2 - mapped on +DATA
With the above configuration in place I have manually corrupted +OCR, +DATA diskgroups with dd command. I used this command to completely corrupt +OCR disk group.
dd if=/dev/zero of=/dev/asm-disk1. I have manual backups as well as automatic backups of OCR and Vote disk. I am not using ASMLib.
I followed this link:
http://docs.oracle.com/cd/E11882_01/rac.112/e17264/adminoc.htm#TDPRC237
When I tried to recover OCR file, I could not do so as there is no such diskgroup which ASM can restore the OCR, Voting disk to. I could not Re-create OCR and DATA diskgroups as I cannot connect to ASM instance. If you have a solution or workaround for my situation please describe it. That will be greatly appreciated.
Thanks and Regards,
Suresh.

Please go through the following document which have the detailed steps to restore the OCR
How to restore ASM based OCR after complete loss of the CRS diskgroup on Linux/Unix systems [ID 1062983.1]

RE: Creation of two oracle database in Single ASM Disk group

IS it possible to create two oracle database in Single ASM Disk group. if it is possible how?.
Giri

All you have to do is to create a tablespace at the most minimumlevel and your db would become a client of the disk group. Other than that, you can migrate your db tothe disk group and it would be then start using the same disk group shared by another database for its use also.
HTH
Aman....

What is the usable space of normal redundancy disk group with two uneven capacity fail groups

Hi,
I have a normal redundancy disk group (DATA) with two uneven capacity fail groups (FG1 and FG2). FG1 size is 10GB and FG2 size is 100GB.
In this case what will be the usable space of the disk group (DATA)? is it 10G or 55G?
Thanks,
Mahi

Please, don't duplicate post with same matter.
This question was answered in your previous thread.
Re: ASM normal redundancy disk group

Need for multiple ASM disk groups on a SAN with RAID5??

Hello all,
I've successfully installed clusterware, and ASM on a 5 node system. I'm trying to use asmca (11Gr2 on RHEL5)....to configure the disk groups.
I have a SAN, which actually was previously used for a 10G ASM RAC setup...so, reusing the candidate volumes that ASM has found.
I had noticed on the previous incarnation....that several disk groups had been created, for example:
ASMCMD> ls
DATADG/
INDEXDG/
LOGDG1/
LOGDG2/
LOGDG3/
LOGDG4/
RECOVERYDG/
Now....this is all on a SAN....which basically has two pools of drives set up each in a RAID5 configuration. Pool 1 contains ASM volumes named ASM1 - ASM32. Each of these logical volumes is about 65 GB.
Pool #2...has ASM33 - ASM48 volumes....each of which is about 16GB in size.
I used ASM33 from pool#2...by itself to contain my cluster voting disk and OCR.
My question is....with this type setup...would doing so many disk groups as listed above really do any good for performance? I was thinking with all of this on a SAN, which logical volumes on top of a couple sets of RAID5 disks...the divisions on the disk group level with external redundancy would do anything?
I was thinking of starting with about half of the ASM1-ASM31 'disks'...to create one large DATADG disk group, which would house all of the database instances data, indexes....etc. I'd keep the remaining large candidate disks as needed for later growth.
I was going to start with the pool of the smaller disks (except the 1 already dedicated to cluster needs) to basically serve as a decently sized RECOVERYDG...to house logs, flashback area...etc. It appears this pool is separate from pool #1...so, possibly some speed benefits there.
But really...is there any need to separate the diskgroups, based on a SAN with two pools of RAID5 logical volumes?
If so, can someone give me some ideas why...links on this info...etc.
Thank you in advance,
cayenne

The best practice is to use 2 disk groups, one for data and the other for the flash/fast recovery area. There really is no need to have a disk group for each type of file, in fact the more disks in a disk group (to a point I've seen) the better for performance and space management. However, there are times when multiple disk groups are appropriate (not saying this is one of them only FYI), such as backup/recovery and life cycle management. Typically you will still get benefit from double stripping, i.e. having a SAN with RAID groups presenting multiple LUNs to ASM, and then having ASM use those LUNs in disk groups. I saw this in my own testing. Start off with a minimum of 4 LUNs per disk group, and add in pairs as this will provide optimal performance (at least it did in my testing). You should also have a set of standard LUN sizes to present to ASM so things are consistent across your enterprise, the sizing is typically done based on your database size. For example:
300GB LUN: database > 10TB
150GB LUN: database 1TB to 10 TB
50GB LUN: database < 1TB
As databases grow beyond the threshold the larger LUNs are swapped in and the previous ones are swapped out. With thin provisioning it is a little different since you only need to resize the ASM LUNs. I'd also recommend having at least 2 of each standard sized LUNs ready to go in case you need space in an emergency. Even with capacity management you never know when something just consumes space too quickly.
ASM is all about space savings, performance, and management :-).
Hope this helps.

Changing VoteDisk Location in Same Disk Group

Hello All,
Greetings !
Oracle Grid Infrastructure 11.2.0.3
RHEL 6.4
I have installed the grid with single disk group having 3 disk DATA, ARCHIVE and OCR. the current location of votedisk is as:
/dev/oracleasm/disks/ARCHIVE [DATA]
it is possible to change the location to
/dev/oracleasm/disks/OCR [DATA]
Please guide.
Thnks & Bst Rgds,
Kapil Relan

Best practice is to make the OCR location normal redundancy with at least 3 members, that way you get 3 copies of the voting disk. There is a bug in the base release of 11.2.0.3 that can cause node to be ejected form the cluster if you only have one voting disk.
More generally you can control which disk group a file is created on but it will be striped across all the disks.
for example in out environment the CRS disk roup contains 3 disks of 2GB each with normal redundancy then two diskgroups with external redundancy DATA and FRA, genrally these will consist of multiple disks with the size being determined by the current requirements and the expected growth.

Oracleasm listdisks is not listing all disk groups and returning "strange special characters" and disks groups are dismounting unexpected

Hi everybody,
I have a 3 node Oracle Cluster with verstion 11.2.0.3.0 installed using ASM/ACFS/ADVM.
Red Hat 5.7 - Kernel 2.6.18-371.12.1.el5 64bits
OracleASM version:
     oracleasm-support-2.1.8-1.el5
     oracleasm-2.6.18-371.12.1.el5-2.0.5-1.el5
     oracleasmlib-2.0.4-1.el5
On may, 2014 we had a physical failure in our storage system and all our disk partitions were completely lost.
The Oracle Grid Infrastructure and Oracle RDBMS haven't needed to be reinstalled because they were healthy.
The Oracle Cluster Registry (OCR) was lost (it was composed by three ASM disk groups in a redundant structure) and after recreation of the OCR disk groups I recover the Oracle Registry information from backup.
All cluster information were recovered (listener, SCAN, VIP, databases and services)
Databases could not be started because all ASM disk groups have been lost and oracle ASM instance (asmcmd -p) was showing all disk groups, but they were all "empty" - the physical partition related with them were recreated.
All the "old" disk groups were dropped, and the "new" disk groups were recreated and all the backups from the databases were restored.
After all services were up, and the environment seems to be OK, I check the healthiness of it, by executing the oracle cluster post-installation tool and others verify tools (crsctl and srvctl), well all returning messages saying that the environment was completely OK and no errors were found or generated (including in many log files I have inspected)
After 2 weeks from the completely recover of the environment, without any error/failure message been received from it, the disk groups started to dismount unexpectedly, from whatever node and not only one specific disk group stops, but any one of them, any time.
I opened a SR in Metalink (Oracle Support) and they conduct me to upgrade RedHat kernel version and OracleASM version.
Simultaneously I opened a Case Solution in RedHat to help me identify the better way to do the upgrade in advantage of the Oracle specifications.
From:
rpm -qa | grep kernel
kernel-devel-2.6.18-274.el5
kernel-headers-2.6.18-274.el5
kernel-2.6.18-274.el5
rpm -qa | grep oracleasm
oracleasm-support-2.1.8-1.el5
oracleasmlib-2.0.4-1.el5
oracleasm-2.6.18-274.el5-2.0.5-1.el5
To:
rpm -qa | grep kernel
kernel-devel-2.6.18-371.12.1.el5
kernel-2.6.18-371.12.1.el5
kernel-headers-2.6.18-371.12.1.el5
rpm -qa | grep oracleasm
oracleasm-support-2.1.8-1.el5
oracleasm-2.6.18-371.12.1.el5-2.0.5-1.el5
oracleasmlib-2.0.4-1.el5
Well, after this upgrade less times the disk groups dismounted, but they continue dismounting from whatever node, any disk group, any time.
So, I opened another SR in Metalink (3-10143566371 still open) and they are conducting me again to upgrade the RedHat kernel version and OracleASM version.
Information about OracleASM:
# oracleasm listdisks
ACFS
FRA
OCR01
OCR02
OCR03
$ asmcmd -p
ASMCMD [+] > ls -l
State    Type    Rebal Name
MOUNTED EXTERN N      ACFS/
MOUNTED EXTERN N      ARCH/
MOUNTED EXTERN N      DEV/
MOUNTED EXTERN N      DIR_LOG/
MOUNTED EXTERN N      JAVA_ARCHIVE/
MOUNTED EXTERN N      MSAF/
MOUNTED NORMAL N      OCR/
MOUNTED EXTERN N      PRD_DATA/
MOUNTED EXTERN N      PRD_REDO1/
MOUNTED EXTERN N      PRD_REDO2/
MOUNTED EXTERN N      PRD_REDO3/
MOUNTED EXTERN N      PRD_REDO4/
MOUNTED EXTERN N      RASTR/
MOUNTED EXTERN N      STAGE/
This is what happens when execute "oracleasm scandisks":
# oracleasm scandisks
Reloading disk partitions: done
Cleaning any stale ASM disks...
Scanning system for ASM disks...
Instantiating disk "ùìÿÿÿÿÿÿÿÿÿÿÿìóæþÿ¥Ï¨®Ð¢"
Unable to instantiate disk "ùìÿÿÿÿÿÿÿÿÿÿÿìóæþÿ¥Ï¨®Ð¢"
Instantiating disk "ü´ñõ
                        ñõúìsö"
Unable to instantiate disk "ü´ñõ
                                ñõúìsö"
~±Ã1~u·}cÿ-Ûg disk "
¾s
~±Ã1~u·}cÿ-Ûinstantiate disk "
¾s
Instantiating disk "à·Öªß³Ö½Þ®hìëÖßßÞÖÛÜØÖÕ"
Unable to instantiate disk "à·Öªß³Ö½Þ®hìëÖßßÞÖÛÜØÖÕ"
Instantiating disk "êËbkî,c
~,XZ±´b¹u²´biÅr"
Unable to instantiate disk "êËbkî,c
~,XZ±´b¹u²´biÅr"
Instantiating disk "
PuTTYPuTTYUnable to instantiate disk "
kÍ3|úùõ/øÊInstantiating disk "u
i)ïìL"
kÍ3|úùõ/øÊe to instantiate disk "u
My question is: "This will really solve the problem?"
Another: "Oracle really understood what is happening and they can help me to solve this problem?"
Final: "Can anyone please help me this problem?"

Hi,
my two cent.
Wait for the SR feedback.
But for the future I advice you to do an ASM Metadata backup to be able to restore this data if you lost
configurations or complete disks and so on.
asmcmd md_backup -b <Pfad>/Filename
and also an ocrconfig backup via crontab.
ocrconfig -local -manualbackup
regards

Could you provide sccripts to add old SAN disk groups to New SAN

Hi,
I'll giv u a brief about my setup. It is 2 node RAC connected to a SAN storage and size of DB is 500GB on Windows 2003. So now they r having a new storage box with 3TBand they asked to migrate this entire setup to new one. So please provide me the detailed doc on this.
I've to migrate Database from OLD SAN to New SAN. Some guys helped me the solution, but i couldnt get clearly. They have told me that
Simply add new LUNs to the existing disk groups. Drop the old SAN LUNs in the disk groups(this merely marks the LUNs to be dropped). Issue a re balance common to move and re stripe the data from the OLD SAN LUNs onto new SAN LUNs.once this operation is completed , ASM will Drop old LUNs from Disk groups and these LUNs can be physically removed. All this can happen with the instance running -it will be obvious of the underlying storage system change being made.
So please provide me the scripts for the above with detailed process how we need to do that and i ma the only person DBA in organisation but i am not much aware about ASM. So please help me out to complete this task.
Even i am new DBA...pls help me out
Regards
Poorna

Hi
Please drop me an email in the below given email id so that I can send you the note which I compiled just now for this.
There is another question also from my end.....
Where is OCR and VD stored ? That also will be in the old storage right ? If that also needs migration to the new storage, then there are some additional steps to migrate OCR and VD.
But for that you will need a small downtime.
Regards,
Mahesh.
[email protected]

Can not find disks when creating ASM disk group (11.0.2.3 on OEL 6)

Hi
I`m trying to install 11.0.2.3 Grid on OEL6.
Every thing is fine until it prompt to ask where I want to put OCR and VOTING DISK. I choose to put them in ASM. So it prompt another window to ask create ASM DISK GROUP.
In this window there was an area called "add disk". There suppose to be some disks listed in this area to chose. But in my case, nothing here. I can not chose disks to add to ASM DISK GROUP.
Below are descriptions of my installation.
Oracle Grid 11.0.2.3
OEL 6 as the platform.
I use two nodes mounting the same NFS. I created some zero-padded files on the NFS directory as the ASM DISKS. (This disks should be showing the the area above)
I install everything using only one account oracle. The group is oinstall and dba
Edited by: Kramer on Jun 5, 2013 8:52 PM

Well as i see your asm_diskstring could be the problem. ASMlib would have been there isnt it , I would want you to stick to default value and then try also I would suggest you to once post the output of the following and lets see whats happening
[root@ora ~]# /etc/init.d/oracleasm scandisks
[root@ora ~]# /etc/init.d/oracleasm listdisks
[root@ora ~]# ls -ltr /dev/oracleasm/disks/*

When the archive disk group and RMAN backup location is full

11.2.0.2 on Solaris 10
2-Node RAC
Sometimes I am faced with a situation where the disk group meant for storing archivelogs is full and the Disk based
RMAN backup location is full as well. What would you do in such a situation ?
This usually happens with our QA/UAT DBs during apps testing of certain type which causes huge amount of redo is generated.
We don't directly backup to tape. The disk based backups are moved to tape every two weeks by our SysAdmin.

Thank you Hemant, Tsharma, Asahideo
If I have free space left in my local filesystem in any of the nodes in my 2-node RAC, I can run something like
-- Untested
BACKUP AS COMPRESSED BACKUPSET ARCHIVELOG ALL DELETE INPUT format '/localNode_pATH/ora_Arch%t_s%s_s%p';and later when the space is freed up in the original RMAN backup location , I can move it there and use CATALOG command to catalog this backup . Right ?

Difference between ASM Disk Group, ADVM Volume and ACFS File system

Q1. What is the difference between an ASM Disk Group and an ADVM Volume ?
To my mind, an ASM Disk Group is effectively a logical volume for Database files ( including FRA files ).
11gR2 seems to have introduced the concepts of ADVM volumes and ACFS File Systems.
An 11gR2 ASM Disk Group can contain :
ASM Disks
ADVM volumes
ACFS file systems
Q2. ADVM volumes appear to be dynamic volumes.
However is this therefore not effectively layering a logical volume ( the ADVM volume ) beneath an ASM Disk Group ( conceptually a logical volume as well ) ?
Worse still if you have left ASM Disk Group Redundancy to the hardware RAID / SAN level ( as Oracle recommend ), you could effectively have 3 layers of logical disk ? ( ASM on top of ADVM on top of RAID/SAN ) ?
Q3. if it is 2 layers of logical disk ( i.e. ASM on top of ADVM ), what makes this better than 2 layers using a 3rd party volume manager ( eg ASM on top of 3rd party LVM ) - something Oracle encourages against ?
Q4. ACFS File systems, seem to be clustered file systems for non database files including ORACLE_HOMEs, application exe's etc ( but NOT GRID_HOME, OS root, OCR's or Voting disks )
Can you create / modify ACFS file systems using ASM.
The oracle toplogy diagram for ASM in the 11gR2 ASM Admin guide, shows ACFS as part of ASM. I am not sure from this if ACFS is part of ASM or ASM sits on top of ACFS ?
Q5. Connected to Q4. there seems to be a number of different ways, ACFS file systems can be created ? Which of the below are valid methods ?
through ASM ?
through native OS file system creation ?
through OEM ?
through acfsutil ?
my head is exploding
Any help and clarification greatly appreciated
Jim

Q1 - ADVM volume is a type of special file created in the ASM DG. Once created, it creates a block device on the OS itself that can be used just like any other block device. http://docs.oracle.com/cd/E16655_01/server.121/e17612/asmfilesystem.htm#OSTMG30000
Q2 - the asm disk group is a disk group, not really a logical volume. It combines attributes of both when used for database purposes, as the database and certain other applications know how to talk "ASM" protocol. However, you won't find any general purpose applications that can do so. In addition, some customers prefer to deal directly with file systems and volume devices, which ADVM is made to do. In your way of thinking, you could have 3 layers of logical disk, but each of them provides different attributes and characteristics. This is not a bad thing though, as each has a slightly different focus - os file system\device, database specific, and storage centric.
Q3 - ADVM is specifically developed to extend the characteristics of ASM for use by general OS applications. It understands the database performance characteristics and is tuned to work well in that situation. Because it is developed in house, it takes advantage of the ASM design model. Additionally, rather than having to contact multiple vendors for support, your support is limited to calling Oracle, a one-stop shop.
Q4 - You can create and modify ACFS file systems using command line tools and ASMCA. Creating and modifying logical volumes happens through SQL(ASM), asmcmd, and ASMCA. EM can also be used for both items. ACFS sits on top of ADVM, which is a file in an ASM disk group. ACFS is aware of the characteristics of ASM\ADVM volumes, and tunes it's IO to make best use of those characteristics.
Q5 - several ways:
1) Connect to ASM with SQL, use 'alter diskgroup add volume' as Mihael points out. This creates an ADVM volume. Then, format the volume using 'mkfs' (*nix) or acfsformat (windows).
2) Use ASMCA - A gui to create a volume and format a file system. Probably the easiest if your head is exploding.
3) Use 'asmcmd' to create a volume, and 'mkfs' to format the ACFS file system.
Here is information on ASMCA, with examples:
http://docs.oracle.com/cd/E16655_01/server.121/e17612/asmca_acfs.htm#OSTMG94348
Information on command line tools, with examples:
Basic Steps to Manage Oracle ACFS Systems

OCR stored in two disk groups

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