Saturday, 19 October 2019

NIMADM Migration Process - 12 Phases

NIMADM Migration Process - 12 Phases

The nimadm command performs migration in 12 phases. Each phase can be executed individually using the -P flag. The nimadm phases are as follows:

1    The master issues an alt_disk_install command to the client which makes a copy of the rootvg to the target disks (coincidentally
     this is Phase 1 of the alt_disk_install process). In this phase altinst_rootvg (alternate rootvg) is created. If a target mksysb
     has been specified, the mksysb is used to create a rootvg using local disk caching on the NIM master.

2    The master runs remote client commands to export all of the /alt_inst file systems to the master. The file systems are exported
     as read/write with root access to the master. If a target mksysb has been specified, the cache file systems are created based on
     the image data from the mksysb.

3    The master NFS mounts the file systems exported in Phase 2. If a target mksysb has been specified, the mksysb archive is restored
     in the cache file systems that were created in phase 2.

4    If a pre-migration script resource has been specified, it is executed at this time.

5    System configuration files are saved. Initial migration space is calculated and appropriate file system expansions are made.
     "bos" is restored and the device database is merged (similar to a conventional migration). All of the migration merge methods are
     executed and some miscellaneous processing takes place.

6    All system filesets are migrated using installp. Any required RPM images are also installed during this phase.

7    If a post-migration script resource has been specified, it is executed at this time.

8    bosboot is executed to create a client boot image, which is written out to the client's boot logical volume (hd5).

9    All mounts made on the master in phase 3 are removed.

10   All client exports created in phase 2 are removed.

11   The alt_disk_install is called again (phase 3 of alt_disk_install) to make final adjustments and put altinst_rootvg to sleep. The
     bootlist is set to the target disk (unless the -B flag is used). If an output mksysb has been specified, the cache is archived
     into a mksysb file and made into a NIM mksysb resource.

12   Cleanup is executed to end the migration. The client is rebooted, if the -r flag is specified.  Note: The nimadm command supports
     migrating several clients simultaneous.


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