IBM TS2340 User Guide - Page 58
Configuring and Unconfiguring Path Failover Support, Primary and Alternate Paths
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AIX Device Driver (Atape) v Delete a license key: dpf_keys -d key Configuring and Unconfiguring Path Failover Support Path failover support is not enabled automatically when the device driver is installed. It must be configured initially on each logical device after installation. When path failover support is enabled for a logical device, it remains set until the device is deleted or the support is unconfigured. The path failover setting is retained even if the system is rebooted. Path failover support can be enabled on all configured devices at one time, or it can be enabled or disabled selectively by logical device. It may be desirable at times to configure some, but not all, logical paths to a device with the support enabled. To enable the support globally on all currently configured devices, run the command: /usr/lpp/Atape/instAtape -a This unconfigures all devices that have path failover set to No, and reconfigures all devices, setting path failover to Yes. To enable or disable the support on a single logical device, use the smit menu to Change/Show Characteristics of a Tape Drive, then select Yes or No for Enable Path Failover Support. The support can also be enabled or disabled using the chdev command, for example: chdev -l rmt0 -aalt_pathing=yes chdev -l rmt0 -aalt_pathing=no Primary and Alternate Paths When the device driver configures a logical device with path failover support enabled, the first device configured always becomes the primary path and PRI is appended to the location field of the device. When a second logical device is configured with path failover support enabled for the same physical device, it configures as an alternate path and ALT is appended to the location field. A third logical device is configured as the next alternate path with ALT appended, and so on. The device driver supports up to 16 physical paths for a single device. For example, if rmt0 is configured first, then rmt1, the lsdev -Cc tape command output is similar to the following: rmt0 Available 20-60-01-PRI IBM 3590 Tape Drive and Medium Changer (FCP) rmt1 Available 30-68-01-ALT IBM 3590 Tape Drive and Medium Changer (FCP) If rmt1 is configured first, then rmt0, the command output is similar to the following: rmt0 Available 20-60-01-ALT IBM 3590 Tape Drive and Medium Changer (FCP) rmt1 Available 30-68-01-PRI IBM 3590 Tape Drive and Medium Changer (FCP) The labeling of a logical device as either a primary or alternate path is for information only, in order to: 1. Be able to identify the actual number of physical devices configured on the system and a specific logical device associated with them. There is only one logical device labeled the primary path for each physical device. However, there may be many (multiple) logical devices labeled as an alternate path for the same devices. 40 IBM Tape Device Drivers Installation and User's Guide