scsimgr SCSI Management and Diagnostics utility on HP-UX 11i v3 (March 2008)

The following table describes when the change of an attribute value is taken into account for
operations, depending on the level where the attribute is changed, and the scope where the attribute
can be set.
Level where the attribute value is changed
Levels where the
attribute is settable
Object instance Global Settable attribute
scope
Global only N/A Immediately
(1)
N/A
Global and object
instance only
Upon re-initialization of
the object instance. For
example LUN open
(2)
.
N/A
Settable attribute scope
and object instance
only
N/A Immediately
(3)
, or
upon initialization of
object instance.
(4)
Object instance only
Immediately
(1)
N/A N/A
1. Immediately: Means the value is taken into account for operation as soon as the semantic of
the attribute permits. For example the max_lunid attribute determines the maximum LUN
identifier probed for target devices which do not support the REPORT LUNS SCSI command.
If the value of this attribute is changed, the new value is used during the next ioscan.
2. The attribute values are reloaded only for the first open. That means if the device is opened
and the attribute is changed, even if another application subsequently opened the device, the
new value will not be taken into account.
3. Starting from the March 2008 release of HP-UX 11i v3, the esdisk driver implements
dynamic update of attributes for the settable attribute scopes it owns. If an attribute is
changed for a settable attribute scope, the new value is taken into account immediately for all
devices covered by the scope.
4. This is valid for HP-UX releases prior to March 2008, or for all settable attribute scopes not
owned by the esdisk driver.
The tunable architecture provides a lot of flexibility when fine tuning the mass storage stack. The
following examples are meant to help understand how the tunable architecture works, how to interpret
attribute values at different levels, and how to use it to optimally solve interoperability problems.
Inheritance of attribute values
The following examples illustrate the rules used to derive attribute current and default values at
different levels.
leg_mpath_enable is an attribute which controls whether built-in multi-pathing is enabled when a
device is accessed through a legacy DSF. This tunable can be set at a global level or for a particular
LUN. By default the SCSI stack explicitly sets this attribute to true at the global level to enable by
default multi-pathing for legacy DSFs of all LUNs.
state is a read-only attribute, which provides the state of the device maintained by the SCSI stack. It is
displayed here to show when the device is closed (state=UNOPEN), or when the device is opened
(state=ONLINE).
In this example disk100 and disk101 are two disk devices on the same system. At system boot
disk100 and disk101 inherit the value of leg_mpath_enable from the global level as shown in the
following scsimgr output.
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