z/VM: CP Commands and Utilities Reference - z/VM - IBM

Table 4. DASD Control Levels
CU
Type
3990-3
3990-6
MB of XSTORE to a user results in CP responding with 4 MB attached.
However, the guest operating system sees 68 MB attached with 64 MB not
configured.
8. Issuing ATTACH XSTORE at initialization suspends virtual machine execution
until XSTORE initialization completes. To avoid this, do one of the following:
v Wait to issue ATTACH XSTORE until XSTORE initialization completes.
v Issue ATTACH XSTORE from a disconnected virtual machine that has been
logged on automatically.
9. Levels of control (SYSCTL/DEVCTL/NOCTL)
Additional Control CCWs
Accepted for DEVCTL
a. The default control level value is normally DEVCTL.
b. The SYSCTL, DEVCTL, and NOCTL operands apply only to DASD on a
cached control unit. If one of these operands is specified for a noncached
DASD, the device is attached and a response is issued stating that the
operand was ignored.
c. Specifying a level of control (NOCTL, DEVCTL, or SYSCTL) for a DASD
attached to a cache storage control unit authorizes CP to accept particular
control CCWs.
Table 4 shows the additional control CCWs CP accepts for a level of
control. The DEVCTL column shows the CCWs CP accepts in addition to
those it accepts for the NOCTL level of control. The SYSCTL column
shows the CCWs CP accepts in addition to those it accepts for the
DEVCTL and NOCTL levels of control.
v Set subsystem mode
– Activate caching for device
– Deactivate caching for device
– Activate DASD fast write
– Deactivate DASD fast write
– Force deactivate DASD fast write
v Perform Subsystem Function
– Establish duplex pair
– Terminate duplex pair
– Suspend duplex pair
– Direct I/O to one device of the duplex pair
Additional Control CCWs
Accepted for SYSCTL
v Set subsystem mode
– Make cache available
– Make cache unavailable
– Force cache unavailable
– Make NVS available
– Make NVS unavailable
– Activate cache fast write
– Deactivate cache fast write
v Perform Subsystem Function
– Destage Modified Tracks
– Set Cache Allocation Parameters
– Suspend/Resume Function
ATTACH
10. When an authorized user issues the GIVE command to transfer control of a
tape drive, the ATTACH command is invoked.
11. The ATTACH command may be used to attach duplex volumes to a guest
virtual machine or the system. Only the primary duplex volume may be
attached to the system. Either the primary volume, the secondary volume, or
both volumes may be attached to a guest virtual machine.
When a duplexed volume is attached to a virtual machine (or to the system),
the responses generated will indicate that the volume was either the primary
duplex volume or the secondary duplex volume of a duplex pair.
12. For a guest virtual machine to establish a duplex pair, both of the affected
volumes must be physically attached to the same 3990 storage control
subsystem, and each volume must be logically attached to that guest with
either DEVCTL or SYSCTL. In order for a guest virtual machine to suspend or
stop a duplex pair, the guest must have DEVCTL or SYSCTL over the primary
volume of the duplex pair.
Chapter 2. CP Commands 31