Aggregating channel paths

When selecting Aggregate channel paths from the Channel Path List against a channel path, HCD offers the possibility of moving all control units from a source channel path to the selected target channel path of the same processor. This is useful for combining several under-utilized channel paths to a single one.

You can aggregate channel paths using the Aggregate channel paths action. The following steps describe the procedure:

1. On the Channel Path List select a channel path and then the Aggregate channel paths action from the context menu or type action code  g  next to the selected CHPID.
2. On the following Aggregate CHPID definition panel you can enter the target channel path ID for the aggregate action.

   *--------------------------Aggregate CHPID ---------------------------*
   |                                                                     |
   |                                                                     |
   | Specify a CHPID to be aggregated with the selected target CHPID.    |
   |                                                                     |
   | Processor ID . . . . : PROC1                                        |
   | Channel subsystem ID : 0                                            |
   | Channel path ID  . . : 00                                           |
   | Channel path type  . : CNC                                          |
   |                                                                     |
   | CHPID to aggregate . . . __  +                                      |
   |                                                                     |
   |                                                                     |
   *---------------------------------------------------------------------*

   HCD displays a list of control units that are currently attached to the source CHPID. If possible, each control unit shows the switch port to which it is connected. Also, the target switch port and the target link address after the aggregate is shown if HCD can determine these. You can select all or a subset of control units to be aggregated to the target CHPID. The selected control units and their attached I/O devices are disconnected from the source CHPID and connected to the target CHPID. The target CHPID may now be connected to a different switch than the source CHPID. Panel Select Control Units to be Aggregated allows you to change the control unit port and link address for the move to the target CHPID.

                     Select Control Units to be Aggregated
                                                                   Row 1 of 12
    Command ===> __________________________________________ Scroll ===> PAGE
   
    Select control units to be aggregated to target channel path. If none is
    selected, no aggregation will take place.
   
      --- Control unit --   -- Source ---    -------- Target -------
    /  Num   Type            Switch   Port    Switch  Port    Linkadd
    _  0000  2107            50       09      50      09      6009
    _  0010  2107            50       10      50      10      6010
    _  0020  2107            50       11      50      11      6011
    _  0030  2107            50       12      50      12      6012
   
    F1=Help F2=Split F3=Exit F4=Prompt F5=Reset
    F7=Backward F8=Forward F9=Swap F12=Cancel F22=Command

   After successful aggregation, a message will be displayed and the Aggregate CHPID panel will remain to allow you to aggregate additional channel paths. If aggregation fails because of validation errors, the validation errors are displayed. If prompting for channel paths for aggregation, HCD will only show the channel paths that allow aggregation without validation errors. Prompting is thus a useful planning aid.

The Aggregate Channel Paths action is only possible if the following prerequisites are fulfilled:

• Source and target channel paths must be different.
• All selected control units connected to the source channel path must be connectable to the target channel path.
• The source channel path must not be connected to a control unit which is already connected to the target channel path. In addition, a link address - unit address - CUADD combination used by a control unit connected to the source channel path must not also be used by a control unit connected to the target channel path.
• Either the source channel path must have the same channel path mode as the target channel path, or all devices accessible by the source channel path must be connected to only one channel path.
• Source and target channel paths must have defined a dynamic switch.
• The user must not lose connectivity by a channel path aggregate action. The source channel path access and candidate list must be the same as or a subset of the target channel path access and candidate list.
• By connecting control units of the source channel path to the target channel path, the defined maximum value for the target channel path type (e.g. maximum number of unit address ranges) must not be exceeded.

As a result of an aggregation action, HCD will:

• Change the preferred channel path of a device to the target channel path if the source channel path was the preferred channel path of the device initially.
• Leave the reachability of devices by logical partitions unchanged.
• Move the CTC control units of the source channel path port to the entry port to which the target channel is connected.