Modify IO settings of input/output devices
Component: | BS2000 |
Functional area: | Device management |
Domain: | DEVICE |
Privileges: | OPERATING |
Routing Code: | G |
Function
Using the MODIFY-IO-OPTIONS command the system support can modify the following IO settings of the input/output devices:
- Timeout value for IO monitoring.
Changes to timeout values are suggested for specific actions that might cause time delay in the execution of an IO request (e.g. during the online update of RAID system’s firmware). Upon completion of these actions the default timeout values should be restored.
- FastDPAV options for disks, if FastDPAV is supported in the system.
In connection with FastDPAV an additional performance improvement can be reached for VM-shared disks.
Selecting a FastDPAV alias device as preferred device for an IO request can increase the performance additively, as the alias devices are assigned exclusively to the guest systems and therefore the overhead of IO execution by the VM2000 hypervisor for these devices is not applied.
The setting of this option is common for all VM-shared disks that are assigned to the system.
In VM2000 operation mode, the command MODIFY-IO-OPTIONS enables the modification of the options in all guest systems that support this command, if it is entered in the Monitor System (VM1),
The command /SHOW-IO-OPTIONS shows the current settings of the option values.
Format
MODIFY-IO-OPTIONS | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Operands
UNIT = alphanum-name_2..2 / x-text_4..4 / *ALL / *CONTROLLER(...) / *DEVICE-RANGE(...)
Specifies the devices, for which the IO settings are to be modified.
UNIT = alphanum-name_2..2 / x-text_4..4
2- or 4-character mnemonic device code of the device.
UNIT = *ALL
The modification is applied to all devices. The combination UNIT=*ALL and TIMEOUT = <integer> is rejected.
UNIT = *CONTROLLER(...)
The modification is applied to all devices of a controller.
NAME = <alphanum-name 2..2> / <x-text 4..4>
2- or 4-character mnemonic device code of the controller.
UNIT = *DEVICE-RANGE(...)
The modification is applied to a group of devices.
The mnemonic device codes specified in this range must not allover belong to generated devices. If the device does not exist, the processing continues with the following mnemonic. Based on the mnemonic of the first device (FROM operand), the mnemonics of the following devices are determined by adding 1 for 4-character (hexadecimal) mnemonics until the mnemonic of the TO operand is reached. In the case of 2-character (alphanumeric) mnemonics, the subsequent mnemonics are created in ascending lexicographical order, that means letters before digits (A, B, ...,Z, 0, 1, ..., 9). The range is limited to 256 mnemonics. The range may not exceed the highest mnemonic FFFF or 99 respectively.
FROM = <alphanum-name 2..2> / <x-text 4..4>
2- or 4-character mnemonic device code of the first device.
TO = <alphanum-name 2..2> / <x-text 4..4>
2- or 4-character mnemonic device code of the last device.
TIMEOUT = *UNCHANGED / *SYSTEM-DEFAULT / <integer 16..86400 >
Specifies the timeout value, that shall be used for the devices specified by the UNIT operand.
The timeout value only refers to devices and is independent of the input/output paths. If a device is connected through several controllers and if the timeout values are modified for several of the controllers, then it is always the most recent setting that takes effect for the device.
Changes to timeout values should only be effective for a limited time and for specific actions (e.g. during the online update of RAID system’s firmware). The default timeout values should then be restored using TIMEOUT= *SYSTEM-DEFAULT.
TIMEOUT = <integer 16..86400 >
Specifies the new timeout value in seconds. The value will be rounded up to a multiple of 8.
TIMEOUT = *SYSTEM-DEFAULT
The system default timeout value is set. The value depends on the device type. It can be determined with the command /SHOW-IO-OPTIONS.
FAST-DPAV = *UNCHANGED / *PARAMETER(...)
Specifies settings for FastDPAV.
FAST-DPAV = *PARAMETER(...)
PREFERRED-DEVICE = *BASE-DEVICE / *ALIAS-DEVICE
Specifies the order of the selection of base device and alias devices for the IO execution of a VM-shared disk, if FastDPAV is supported in the system.
The setting is accepted independently of the devices specified in the UNIT operand.
If FastDPAV is not supported in the system, the command is rejected.
PREFERRED-DEVICE = *BASE-DEVICE
If no IO is running on the base device, this one is chosen for an incoming IO request. If an IO is already running on the base device, a new IO request is started on an alias device, provided there is one available. This is the system preset device selection.
PREFERRED-DEVICE = *ALIAS-DEVICE
If no IO is running for the device neither on the base nor on a alias device, a new IO request is started on an alias device, provided there is one available. If there is already an IO request running for this device, a new one will be started on the base device, if there is no IO running on it or if no (further) alias device is available.
This device selection mode can improve the IO performance, if there are sufficient alias devices available. It may be unfavourable, if volumes with low IO rate occupy the alias devices and volumes with higher IO rate have no or too few alias devices at their disposal.
SCOPE = *OWN-SYSTEM-ONLY / *VM2000-GLOBAL
Specifies how the command is to be executed in VM2000 operation mode.
SCOPE = *OWN-SYSTEM-ONLY
The command is executed in the local system only.
SCOPE = *VM2000-GLOBAL
If entered in the Monitor System (VM1), the command is executed in all guest systems that support this command. If entered in another guest system, the command is rejected.
Command Return Codes
(SC2) | SC1 | Maincode | Meaning |
|---|---|---|---|
0 | CMD001 | Command processed successfully | |
64 | NDI0711 | UNIT not found | |
64 | NDI0715 | Device Range invalid | |
64 | NDI0758 | Not privileged for SCOPE=VM | |
64 | NDI0716 | Operand combination invalid | |
64 | NDI0714 | FastDPAV not supported | |
32 | NDI0713 | Internal error | |
32 | NDI0759 | VM communication with error |
Examples
/MODIFY-IO-OPTIONS A500,TIMEOUT=300
% NDI0718 'TIMEOUT' VALUE OF 'DEVICE' 'A500' MODIFIED
/MOD-IO-OPT *ALL,FAST-DPAV=*PAR(ALIAS)
% NDI0718 'FAST-DPAV' VALUE OF 'ALL' 'DEVICES' MODIFIED
/MOD-IO-OPT *CONTROLLER(AK),TIME=300,SCOPE=*VM
% NDI0718 'TIMEOUT' VALUE OF 'CONTROLLER' 'AK' MODIFIED % NDI0753 MODIFICATION OF IO OPTIONS COMPLETED AT VM SYSTEM 'VMGUEST3' % NDI0753 MODIFICATION OF IO OPTIONS COMPLETED AT VM SYSTEM 'VMGUEST5' % NDI0757 VM COMMUNICATION FOR IO OPTIONS NOT SUPPORTED BY ' 2' VM SYSTEMS