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NAME : HCPVIUBK
DESCRIPTION: VDEV I/O Assist Utilization Block
DSECT : VIUBK
FUNCTION : To track a device's utilization of I/O Assist
LOCATED BY : VDEVIUBK Field of VDEV - Virtual Device Control Block
CREATED BY : VIUBK's are dynamically created by HCPIAXBL for I/O
Assist eligible devices when we log on, attach a
device, redefine a device (if VIUBK did not already
exist).
DELETED BY : VIUBK's are deleted by HCPIAXBL when a redefine makes
a device ineligible, or by HCPVDBDL when it deletes the
associated VDEV.
SERIALIZED : The VDEVLOCK should be held when referencing VIUBK fields.
RELOCATION CONSIDERATIONS : None
NOTES :
- When the VIUBK is first built, VIUCNTOT is
incremented.
- A transition from IN to OUT is considered to pass
through a LEAVING state, but to spend no time there.
- (Therefore) The counters VIUCNTOT, VIUCNTIN and
VIUCNTLV will all be within one of each other. The
state of the device could be determined from these
counters - When CNTOT is one greater than the other
two, the device should be in the OUT state. When
CNTLV is one less than the other two, the device
should be in the IN state. When they are all equal,
the device should be in the LEAVING state. If this
is not true, this should be considered an error in
the code maintaining the counters.
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