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How many partners?
ASM provides data redundancy by placing mirrored extent copies on partner disks in different failgroups. Each ASM disk, in a redundant disk group of course, would have up to 8 partner disks (up to 10...
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ASM disk header
ASM disk header is probably the best known piece of ASM metadata. Chances are you learned about it when it was damaged or lost and hopefully Oracle Support was able to get you up and running. In this...
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ASM Toolbox
Here are the ASM tools I recommend you get familiar with.asmcmd - command line interface to ASMWhen ASM was released the asmcmd was useless. Today, in version 11gR2, the asmcmd is a truly versatile and...
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amdu - ASM Metadata Dump Utility
The ASM Metadata Dump Utility - better knows as amdu - is used by Oracle Support and Oracle Development to diagnose and sometimes resolve ASM issues. It can be used to print ASM metadata and extract...
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Offline or drop?
When an ASM disk becomes unavailable, ASM drops it from the disk group, right? Well, that depends on the ASM version and on the disk group redundancy. An external redundancy disk group would be simply...
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Rebalancing act
ASM ensures that file extents are evenly distributed across all disks in a disk group. This is true for the initial file creation and for file resize operations. That means we should always have a...
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Forcing the issue
Some ASM commands have the "force" option that allows the administrator to override a default behaviour. While some uses of the force option are perfectly safe and indeed required, some may render your...
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ASM file number 1
ASM file number 1 - the file directory - keeps track of all files in the disk group. As disk groups are independent storage units, each will have its own file directory.While this is an internal file,...
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ASM file number 2
ASM file number 2 - the disk directory - keeps track of all disks in the disk group. As disk groups are independent storage units, each disk group will have its own disk directory.As far as ASM is...
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ASM file number 3
When ASM needs to make an atomic change to multiple metadata blocks, a log record is written into the Active Change Directory (ACD), which is ASM metadata file number 3. These log records are written...
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ASM file number 4
Some long-running ASM operations, like rebalance, drop disk, create/delete/resize file, cannot be described by a single record in the active change directory. For those operations ASM uses the...
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ASM file number 5
The Template Directory - ASM file number 5 - contains information about all file templates for the disk group.There are two types of templates - system and user created. The default (system) templates...
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ASM file number 6
The alias directory - ASM file number 6 - provides a hierarchical naming system for all the files in a disk group.A system file name is created for every file and it is based on the file type,...
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ASM file number 7
ASM metadata file number 7 - volume directory - keeps track of files associated with ASM Dynamic Volume Manager (ADVM) volumes.An ADVM volume device is constructed from an ASM dynamic volume. One or...
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ASM file number 8
The disk Used Space Directory (USD) – ASM file number 8 - maintains the number of allocation units (AU) used per zone, per disk in a disk group. The USD is split into a set of Used Space Entries (USE)....
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ASM file number 9
The attributes directory - ASM file number 9 - contains metadata about disk group attributes. The attributes directory exists only in disk groups where COMPATIBLE.ASM is 11.1 or higher.Disk group...
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ASM files number 10 and 11
ASM metadata file number 10 is ASM user directory and ASM file number 11 is ASM group directory. These are supporting structures for ASM file access control feature.ASM file access control can be used...
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ASM files number 12 and 254
The staleness directory (ASM file number 12) contains metadata to map the slots in the staleness registry to particular disks and ASM clients. The staleness registry (ASM file number 254) tracks...
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ASM in Exadata
ASM is a critical component of the Exadata software stack. It is also a bit different - compared to non-Exadata environments. It still manages your disk groups, but builds those with grid disks. It...
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Exadata motherboard replacement
This photo story is about a motherboard replacement in an Exadata X2-2 database server (Sun Fire X4170 M2).While setting up a half rack Exadata system, we discovered a problem with the motherboard in...
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