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Chapter 2. Migration methods 7
2.3.1 Migration installation
Migration installation is the default method to move from AIX 3.2 or any release of AIX Version
4 to AIX 5L. During a migration, the installation process determines which optional software
products are installed on the existing version of the operating system. Any configuration file
that cannot be migrated will be saved in a specific directory under /tmp. System messages
will inform you of the location of the saved files. Information will also be stored in the system
installation log /var/adm/ras/devinst.log.
The migration process attempts to preserve all user configuration, while moving the operating
system to a new level of software.
The advantage of a migration installation compared to a new and complete overwrite is that
many files are preserved. This includes almost all directories, such as /home, /var, /usr, the
root volume group, logical volumes, system configurations, and previously installed software.
The only file system that will be refreshed after the migration is /tmp. You can easily avoid
losing information you have stored in this directory by copying the important information to
another directory before the migration and move it back afterwards. Additionally, after the
migration, you can import your user volume groups. It is probably the easiest way to upgrade
your system to AIX 5L while maintaining all customized information and configuration.
Another migration advantage, especially if you need to minimize the downtime of your
system, is that there are fewer reconfiguration tasks to perform when the migration process
has completed.
If an application has the requirement to use a large file system in a server environment (up to
32 TB) you must use the JFS2 file system, which was introduced with AIX 5L. By doing a
migration installation to move from AIX 4.3.3 to AIX 5L, existing JFS file systems cannot be
converted to JFS2 file systems. This is only possible for new and complete overwrite and
preservation installations. If installed graphics software support or other additional software,
selected from the installation menu during an overwrite installation, this option is not available
at migration installation time. However, after the migration is completed, you can select
additional filesets to install from various CDs or, alternatively, you can prepare software
resources over the network before migrating your system and install them after the migration
process completes.
2.3.2 New and complete overwrite installation
The new and complete overwrite installation should be used to install AIX 5L Version 5.1 on a
new system or on a system on which you do not wish to preserve the existing version of AIX,
its configuration, and possibly some of the user data. The main advantage of this method is
that your resulting AIX 5L Version 5.1 installation is cleaned of obsolete data. On the other
hand, the system will need to be reconfigured. The complexity of your installation will
determine the amount of additional work required. This work must be evaluated before
choosing such a method.
User-defined volume groups (non-root volume groups) will be preserved and will remain there
after the new installation. You should import these volume groups and mount the file systems
created on them.
Note: After a migration installation, if you want to install the next recommended
maintenance level of AIX, use the SMIT update_all fast path or the install_all_updates
command to update the filesets currently installed.