Managing tape multipath

Manage tape multipath with Dedicated Service Tools (DST) or System Service Tools (SST).

Tape multipath configurations are managed by using the DST or SST tools and use the same interfaces that are used for managing disk device multipath configurations.

Viewing the multipath connections

From the Use Dedicated Service Tools or System Service Tools display, select Start a Service Tool.
From the Start a Service Tool display, select Hardware service manager.
From the Hardware Service Manager display, select Packaging hardware resources (systems, frames, cards,...).
Find the packaging resource for the Tape Subsystem that you want to work with and select Hardware contained within package to show the Devices Contained Within Package display.

The tape multipath information is shown as part of a “Tape Subsystem” package.

There is a tape subsystem package for each logical tape library.
There is one tape subsystem package for all of the stand-alone tape drives.
The tape subsystem package is there even when there is only one path.

The first view of the Devices Contained Within Package display shows the Logical Address and adapter Location information for each path to each device. Use function key F11 to switch the view to show the device resource name, device status, and path count information for each

Viewing and changing the preferred path device

The preferred path device is the device resource whose path is selected at vary on time, or during allocation of the device to a tape library, for tape I/O. If the path to the preferred path device is not available, then one of the alternative paths to that device is selected instead.

Note: Before the preferred path for a tape device can be changed:

It must be varied off.
It must not be in use by Dedicated Service Tools.
It must not be associated with a varied on Network Service Description.
Any tape resources within a tape library device must be deallocated from the tape library.

Using the Hardware Service Manager to view or change the preferred path device

From the Use Dedicated Service Tools or System Service Tools display, select Start a Service Tool.
From the Start a Service Tool display, select Hardware service manager.
From the Hardware Service Manager display, select Packaging hardware resources (systems, frames, cards,...).
Find the packaging resource for the Tape Subsystem that you want to work with and select Hardware contained within package.
From the Devices Contained Within Package display, select Paths to multiple path device for the device for which you want to set the preferred path.

The first device resource in the list of resources that are shown in the Paths to Multiple Path Device display is the current preferred path device. Selecting option 9 next to a resource in the list and pressing enter moves that device resource to the top of the list. It also selects it to be the preferred path device the next time the device description is varied on, or during allocation of the device to a tape library, or when the partition is restarted.

Note: For IBM i 7.2 option 9 is a hidden option.

Using the iotapepaths Advanced Analysis macro to change the preferred path

With IBM® i 7.2 PTF MF65029, IBM i 7.3 PTF MF65030, and IBM i 7.4, support was added for changing the preferred path using the iotapepaths Advanced Analysis macro.

From the Use Dedicated Service Tools or System Service Tools display, select Start a Service Tool.
From the Start a Service Tool display, select Display/Alter/Dump.
From the Display/Alter/Dump Output Device display, select Dump to printer or Display/Alter storage.
From the Select Data display, select Licensed Internal Code (LIC) data.
From the Select LIC Data display, page down and select Advanced analysis.
From the Select Advanced Analysis Command display, type a 1 in the Option field next to the blank line and enter iotapepaths as the Command.
From the Specify Advanced Analysis Options display:
- Enter the resource name of the device to make the preferred path device and the option -PREFER to change the preferred path.

Verifying a path connection

Dedicated Services Tools or System Service Tools can be used to verify that there is a working path to a device for a specific IOP.

From the Use Dedicated Service Tools or System Service Tools display, select Start a Service Tool.
From the Start a Service Tool display, select Hardware service manager.
From the Hardware Service Manager display, select Logical hardware resources (buses, IOPs, controllers,...).
From the Logical Hardware Resources display, select System bus resources.
Find the Virtual IOP with the path to the device that you want to verify and select Resources associated with IOP.
Find the specific tape unit that you want to verify the path connection for and select Verify.

If the test completes successfully, there is a working path to the device by the virtual IOP you selected in step 5.

If the test fails with the message Device is busy, make the device ready and run the test again, communication to the device worked, but it is assigned to a different active path on the same partition. In this case, there is also a working path to that device by the virtual IOP you selected in step 5.

Retrieving detailed information about the multipath configuration

The iotapepaths Advanced Analysis macro can be used to display or print detailed information about the multipath configuration. Use the following steps to run the iotapepaths Advanced analysis macro:

From the Use Dedicated Service Tools or System Service Tools display, select Start a Service Tool.
From the Start a Service Tool display, select Display/Alter/Dump.
From the Display/Alter/Dump Output Device display, select Dump to printer or Display/Alter storage.
From the Select Data display, select Licensed Internal Code (LIC) data.
From the Select LIC Data display, page down and select Advanced analysis.
From the Select Advanced Analysis Command display, type a 1 in the Option field next to the blank line and enter iotapepaths as the Command.
From the Specify Advanced Analysis Options display:
- Leave the Options field blank and press Enter to retrieve path information for all devices, or:
- Enter a resource name to filter the information retrieved.
  1. IOP resource name - Retrieve tape resources configured on this IOP.
  2. Tape Library resource name – Retrieve all tape resources associated with this logical tape library.
  3. Tape Device resource name – Retrieve all the paths to this resource.