Types of hardware unit
The following types of hardware unit are included in a configuration:
the CPUs (central processing units)
the channels (CHN), which are defined by means of the IOGEN statement CHN
the multidevice controllers (CTL), which are defined by means of the IOGEN CTL statement (tape and disk controllers)
the devices (DVC), which are defined by means of the IOGEN DVC statement
On SUs x86 only channels (CHN) and devices (DVC) are known and visible in BS2000, but no controllers (CTL).
With virtual connections a distinction is made between inner and outer units, which are used for input/output.
The channels (CHN) are the inmost hardware units, the devices (DVC) the outmost. The order of the various hardware units, viewed from the inside to the outside, is as follows CHN - CTL - DVC
Thus when, for example, a direct virtual connection exists between the two hardware units CTL and DVC, CTL is the inner and DVC the outer unit.
States of hardware units
These hardware units can assume the following states:
ATTACHED
The hardware unit is attached to the system and can be used for input/output. This state is set:
after system initialization if the appropriate unit was generated in the hardware generation with IOGEN with the attribute “A” (e.g. DVC A0,CB,A,(...))
after system initialization if the appropriate unit was modified in the startup parameter service with the IOCONF statement MOD-IO-UNIT ..., STATE=ATT
after successful invocation of the ATTACH-DEVICE (ATT) command.
after successful invocation of the ADD-IO-UNIT command (with STATE=*ATTACHED)
ATTACH-PENDING
Attachment is performed for a disk or tape device. The hardware unit cannot yet be used for input/output. If the reconfiguration job is executed, the hardware unit assumes the ATTACHED state.
If the reconfiguration job cannot be executed, the hardware unit is placed in the DETACHED state (see section “Special information on tape devices” in chapter "Special information on magnetic tape and disk devices").
This state is set during execution of input/output operations to determine control and device data and to reserve MTC devices.
DETACHED
The hardware unit is detached from the system and cannot be used for input/output. The DETACHED state is further subdivided into:
DETACHED EXPLICITLY. This state is set:
after system initialization if the relevant unit was generated in in the hardware generation with IOGEN with the attribute “D” (e.g. DVC_A0,CB,D,(...))
after system initialization if the relevant unit was modified in the startup parameter service with the IOCONF statement MOD-IO-UNIT ..., STATE=DET
after successful invocation of the DETACH-DEVICE (DET) command (DET)
after automatic reconfiguration by the operating system
after system initialization if a hardware unit is recognized as “offline”.
DETACHED IMPLICITLY
All internal connections of the appropriate unit are in the REMOVED state.
DETACH-PENDING
The unit is still allocated by a task or the system and is no longer available after the end of allocation. Further allocation attempts are not permitted. The DETACH-PENDING state occurs generally only during a specified wait time (operand FORCE=NO...) in the DETACH-DEVICE command. It can also occur if a DETACH-DEVICE command is issued with the FORCE=*YES operand for a magnetic tape cartridge device (see section “Special information on tape devices” in chapter "Special information on magnetic tape and disk devices").
If the reconfiguration job can be carried out during the wait time, the unit is placed in the DETACHED state, otherwise it (re-)enters the ATTACHED state. The DETACH-PENDING state is subdivided into:
DETACH-PENDING EXPLICITLY
This state is set if the unit is directly detached.DETACH-PENDING IMPLICITLY
This state is set if no inner connections of this unit are in the INCLUDED state and at least one is in the REMOVE-PENDING state.
INVALID
The device cannot be used nor can it be reconfigured (attached).
Example: The device has been removed with REMOVE-IO-UNIT.
ENABLED
Possible state of a FastDPAV alias device: The FastDPAV alias device can be used for input/output.
The state is set:
- in native mode, if the FastDPAV alias device has not been explicitly detached (DETACH-DEVICE command).
- in VM mode, if the FastDPAV alias device has been assigned to the virtual machine and not been explicitly detached afterwards (DETACH-DEVICE command).
DISABLED
Possible state of a FastDPAV alias device: The FastDPAV alias device cannot be used for input/output.
The state is set:
- in native mode, if the FastDPAV alias device has been explicitly detached (DETACH-DEVICE command).
- in VM mode, if the FastDPAV alias device has not been assigned to the virtual machine or has been explicitly detached afterwards (DETACH-DEVICE command).