Example 2: Adding a String of Shared 3490 Tape Drives to Two Logical Partitions

This example shows you how to take an existing unshared channel path, change it to a channel path shared between two logical partitions, add an ESCON control unit, and add a string of 3490 tape drives, using the sample IOCP source file in Sample I/O Configuration Program File.

In this example, we will delete channel path 2C, define it again as a channel path shared between two logical partitions, add an ESCON control unit, and add a string of 3490 tape drives. As in Example 1, we will be using the Lock-Step process. Thus, the process remains the same, only the dynamic I/O commands will change.

To change the channel path, add the control unit, and add the tape drives:

Update the IOCP source file (2097 IOCP A):
1. Enter:
```
   xedit  2097  iocp
```
2. Change the existing channel path definition (CHPID macroinstruction) for channel path 2C to:
```
  CHPID PATH=(2C),TYPE=CNC,SHARED
```
3. Add the following CNTLUNIT macroinstruction between the control unit definitions for control units 1B00 and 2D00:
```
  CNTLUNIT CUNUMBR=2C00,PATH=(2C),UNIT=3490,UNITADD=((00,16))
```
4. Add the following IODEVICE macroinstruction between the I/O device definitions for devices 1B00 and 2D00:
```
  IODEVICE ADDRESS=(2C00,16),CUNUMBR=2C00,UNIT=3490
```
5. File the changes back onto your A-disk or SFS directory.
Verify the newly-changed IOCP source file (2097 IOCP A) using the IOCP utility:
```
   iocp  2097  ( nowrt 
```
We specified the NOWRT option because we do not want to write the newly-generated IOCDS file to the SE hard disk until we verify that there are no syntax, semantic, or processor-specific errors in the IOCP source file. You can find all the errors in the IOCP configuration report (2097 LISTING A).

If there are no errors from the IOCP utility, you can continue to the next step. If there are errors from the IOCP utility, you must update the IOCP source file and validate it again.

For more information about the IOCP configuration report and the return codes generated by the IOCP command, see the IOCP manual of your specific processor.
Use the dynamic I/O commands to change the software's (z/VM's) and the hardware's (HSA's) view of the I/O configuration. You can find complete descriptions of all the dynamic I/O commands listed in this example in the z/VM: CP Commands and Utilities Reference.
As stated previously, channel path 2C is an existing channel path. So, we need to delete channel path 2C, define it again as a channel path shared between two logical partitions, add an ESCON control unit, and add a string of 3490 tape drives.
1. Turn configuration mode on using the following command:
```
   set  configmode  on
```
2. Delete existing control unit 2C using the following command:
```
   delete  chpid  2c
```
3. Define channel path 2C again as a channel path shared between logical partitions CAMBVM3 and CAMBVM4 with both logical partitions having initial access using the following command:
```
def chpid 2c pchid 120 type escon shared acc cambvm3 cambvm4 init cambvm3 cambvm4
```
  Note: In this example, logical partitions CAMBVM3 and CAMBVM4 are both running z/VM®.
4. Add the ESCON control unit and attach it to channel path 2C using the following command:
```
   define  cu  2c00  type  escon  unit_address  00-0f  chpid  2c
```
5. Add the string of tape drives and assign them to control unit 2C00 using the following command:
```
   def device 2c00-2c0f unit_address 00 cu 2c00 partition cambvm3 cambvm4
```
6. Turn configuration mode off using the following command:
```
   set  configmode  off
```
  At this point, you have defined the changed channel path, new control unit, and new I/O devices. Now, you must vary the channel path on in both logical partitions: CAMBVM3 and CAMBVM4.
7. You can vary the channel path on using the following command in each logical partition:
```
   vary  online  chpid  2c
```
  At this point, if your z/VM system is set up to initialize new devices as they are added to a running system, CP initializes the devices and brings them online. To tell CP to initialize new devices as they are added to a running system, use the CP SET NEW_DEVICES INITALIZE_WHEN_ADDED ON command or add a FEATURES ENABLE NEW_DEVICES_INITIALIZED_WHEN_ADDED statement to your system configuration file.
  
  If your z/VM system does not initialize new devices as they are added to a running system, you must vary on the new devices using the following command:
```
   vary  online  2c00-2c0f
```
  At this point, you have a shared channel path, an ESCON control unit, and 16 3490 tape drives, all of which are online.
Generate the final version of the IOCDS file and write it to the SE hard disk:
```
   iocp  2097  ( wrta2  
```
We specified the WRTA2 option to write the IOCDS file to slot A2 on the SE hard disk.
Make the newly-generated IOCDS file the active IOCDS file using the following command:
```
   set  iocds_active  a2
```

After completing these steps, you will have dynamically changed the I/O configuration of the software (z/VM) and the hardware (in the HSA). Also, you will have created a new active IOCDS file that matches the dynamic I/O changes, thereby ensuring that these changes will survive a power-on reset (POR) of the processor.

Note: In this example, z/VM was the operating system in both logical partitions. If you have z/VM making dynamic I/O changes that affect another logical partition and that logical partition is not running z/VM, then please consult the documentation for the other operating system for instructions on how to bring a channel path and the devices online.