A device alias supports the following two modes:
Basic mode: When operating in basic mode, which is the default, the device alias is immediately expanded to a pWWN. This operation continues until the mode is changed to enhanced. In basic mode, when device aliases are changed to point to a new HBA, for example, that change is not reflected in the zone server. Users must remove the previous HBA’s pWWN, add the new HBA’s pWWN, and then reactivate the zone set.
Enhanced mode: When operating in enhanced mode, applications accept a device alias name in its native format. Instead of expanding the device alias to a pWWN, the device alias name is stored in the configuration and distributed in its native device alias format. So, applications such as zone server, PSM, or DPVM can automatically keep track of the device alias membership changes and enforce them accordingly. The primary benefit of operating in enhanced mode is that you have a single point of change.
Whenever you change device alias modes, the change is distributed to other switches in the network only if device alias distribution is enabled, or on. Otherwise, the mode change takes place only on the local switch.
If two fabrics running in different device alias modes are joined together, the device alias merge fails. There is no automatic conversion to one mode or the other during the merge process. In this situation, you must select one mode over the other. Before changing from enhanced to basic mode, you must first explicitly remove all native device alias-based configurations from both local and remote switches or replace all device alias-based configuration members with the corresponding pWWN. If you remove a device alias from the device alias database, all applications automatically stop enforcing the corresponding device alias.
Renaming the device alias not only changes the device alias name in the device alias database but also replaces the corresponding device alias configuration in all of the applications. When a new device alias is added to the device alias database, and the application configuration is present on that device alias, it automatically takes effect.
Device Alias Distribution
By default, device alias distribution is enabled. The device alias feature uses CFS to distribute the modifications to all switches in a fabric.
If device alias distribution is disabled, database changes are not distributed to the switches in the fabric. The same changes would have to be performed manually on all switches in the fabric to keep the device alias database up-to-date. Database changes immediately take effect, so there would also not be any pending database and commit or abort operations. If you have not committed the changes and you disable distribution, a commit task will fail. But if you modify the device alias configuration, you will need to commit or discard the changes because the fabric remains locked during this period. Device alias database changes are validated with the applications. If any of the applications cannot accept the device alias database changes, those changes will be rejected; this applies to device alias database changes resulting from either a commit or merge operation.