Thursday, April 8, 2010

What is ODM?

Object Data Manager is database for storing system information. Physical and logical device information is stored and maintained as objects. For safety reason ODM data is stored in binary format.

Most System object classes and objects are stored in the /usr/lib/objrepos directory, ODM information is stored in three directories as follows:

/etc/objrepos --- Software can’t be shared (self)
/usr/lib/objrepos --- Software can be share among several systems (Standalone)
/usr/share/lib/objrepos --- can be shared for different hardware architecture (other architecture)

The basic components of the ODM are object classes and objects. To manage object classes and objects, you use the ODM commands and subroutines.

System data managed by the ODM includes:

Ø Device configuration information
Ø System vital product data for installation and update procedure
Ø System resource controller information
Ø TCP/IP configuration data
Ø Error log and Dump information
Ø SMIT menus and commands
Ø Network installation Manager information

In the area of device configuration, the ODM contains information about all configured physical volumes, volume groups and logical volumes. This information mirrors the information found in the VGDA. The process of importing a VGDA, for Example, involves copying the VGDA data for the imported volume group into the ODM. When a volume group is exported, the data held in the ODM about the volume group is removed from the ODM database.

There are 2 types of ODM device database files

1) Predefined device information ,which contains all supported devices
2) Customized device information, which contains all devices that are actually attached to the system.

ODM Commands:

Odmadd---Adds objects to an object class.
Odmchange---Changes specific objects in a specified object class.
Odmcreate---Creates empty object classes.
Odmdelete---Removes objects from an object class.
Odmdrop---Removes an entire object class.
Odmget---Retrieves objects from object classes.
Odmshow---Displays the description of an object class.

Examples:
#odmshow CuDv ---- The object class definition for the Customized Device Database (CuDv)
#odmshow PdDv ---- The object class definition for the Predefined Device Database (PdDv)

Software vital product database information contains
1) LPP contains information about installed software product
2) Inventory contains files associated with software product
3) Product information about installation/updates of software product
4) History – historical information about software.

Whenever installing a product or update in AIX, installp command uses the ODM to maintain the software vital product database.
Things to keep in mind
********************
1. Importing a VG involves copying the VGDA data for the imported volume group into the ODM.
2. Resynchronize the ODM. The VG must be active.synclvodm rootvg : synchronizes the device configuration database with the LVM information for rootvg (use when the device configuration database is not consistent with the LVM information in the LVCBs and the VGDAs).
3.The PVID is stored on the disk itself and is also stored in the ODM of a machine
when a volume group is created or imported.
4.There exists an ODM object known as the vg-lock. Whenever an LVM
modification command is started, the LVM command will lock the vg-lock for the
volume group being modified. If, for some reason, the lock is inadvertently left
behind, the volume group can be unlocked by running the varyonvg -b
command, which can be run on a volume group that is already varied on.
5. To remove an entry from odm
eg: rmdev -dl hdiskX

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