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This report produces a tabular listing of demand scan
activity in time sequence. The information is summarized by
the number of minutes specified by the user as a run-time
execution parameter. Activity is displayed over the period
of time specified by the user, again as run-time execution
parameters.
INTENDED USE:
When CP needs additional storage to continue processing,
it takes frames from the CP-maintained list of available
frames. If CP cannot find a frame in the available list,
it must take frames away from the virtual systems to
replenish the available list. CP invokes a demand scan
function to replenish the available list when it reaches a
point called the low threshold. The function removes
selected frames from user-owned frame lists, and places
them on the available list. The demand scan function
places frames on the available list until the list
reaches a value called the high threshold. The
demand scan function consists of two passes of various
VMDBKs, and a special emergency pass if the two regular
passes do not successfully replenish the list.
Within each pass, the function examines VMDBKs in an order
that will hopefully have the least impact on a given user
and on the system as a whole. For example, in the first
pass of the function, long-term dormant users are examined
first, followed by short-term dormant users. Next, the
shared frame owned list (including system VMDBK, named
saved systems, discontiguous saved segments, and shared
address spaces) is examined for frames to remove, followed
by the eligible list, and finally the dispatch list. With
each succeeding pass, the function becomes less selective
about which frames to take from users.
The VM Monitor records count indicating at which point in
the demand scan function the available list was
successfully replenished. For example, over a five-minute
period, during an average interval, the Demand Scan
function might complete after scanning the short-term
dormant list in Pass 1, 90.0 times. This report indicates
the average number of times per monitor interval that the
demand scan function completed within a given phase of the
function.
The report is intended to show how far into the Demand
Scan function it is necessary to proceed before the
available frame list is replenished. If numbers start
appearing in the Emergency Pass part of the report, it can
be indicative of a storage-constrained environment.
FORMAT:
A tabular report in chronological order, where each line
represents a summarization of DETAIL data across a user-
specified period of time. The columns within each Demand
Scan Pass represent the average number of times per
monitor interval that the Demand Scan function completed
in that phase. They are ordered from left to right in the
same order that the system algorithm proceeds through the
various lists of VMDBKs. The following abbreviations are
used for column headings with each pass:
LTD Long Term Dormant VMDBKs
STD Short Term Dormant VMDBKs
SYS/SHAR System VMDBK, Shared Storage VMDBKs (NSSs and
DCSSs), and Shared Address Spaces
ELST Eligible List VMDBKs
DLST Dispatch List VMDBKs
The final three columns of the report show the following
averages for the reporting interval (these are not
totals):
SCAN NCMP - The average number of times per monitor
interval that the Demand Scan Function did not
complete successfully.
ALIST EMPTY - The average number of times per monitor
interval that the available frame list was empty.
DFRD TASKS - The average number of tasks per monitor
interval that were deferred while waiting for a page
of real storage. This represents the average number
of requests for real frames that have not been
satisfied yet because no frames are available.
An example of this report is shown in Figure 3-5.
INQUIRY ID:
Tabular Report: VMXTX4
DATA SOURCE (File/Timespan):
VMXSPP01 - DETAIL
DATA ELEMENTS USED:
SPPLD1CT - DScan Pass 1 Complete Long Term Dormant
SPPDM1CT - DScan Pass 1 Complete Short Term Dormant
SPPSY1CT - DScan Pass 1 Complete SYSTEM VMDBK (* note)
SPPSS1CT - DScan Pass 1 Complete Shared Frame Owned List
SPPEL1CT - DScan Pass 1 Complete Eligible List
SPPDL1CT - DScan Pass 1 Complete Dispatch List
SPPLD2CT - DScan Pass 2 Complete Long Term Dormant
SPPDM2CT - DScan Pass 2 Complete Short Term Dormant
SPPEL2CT - DScan Pass 2 Complete Eligible List
SPPDL2CT - DScan Pass 2 Complete Dispatch List
SPPSSECT - DScan Pass E Complete Shared Frame Owned List
SPPDMECT - DScan Pass E Complete Short Term Dormant
SPPELECT - DScan Pass E Complete Eligible List
SPPSYECT - DScan Pass E Complete SYSTEM VMDBK (* note)
SPPDLECT - DScan Pass E Complete Dispatch List
SPPNOCMP - Demand Scan Not Completed Successfully
SPPALMPT - Times Available List Became Empty
SPPFRQWT - Deferred Tasks Waiting for A Frame
Note: SPPSY1CT and SPPSYECT are only applicable to
systems prior to VM/ESA Release 2.
CALCULATIONS:
The various elements to be reported on are summarized
across processors, using CA MICS summarization, to provide
system-wide totals. CA MICS summarization is then invoked
a second time to summarize across the user-specified time
period, if necessary. Finally, prior to reporting, each
element is averaged by dividing it by the number of
monitor intervals.
USAGE CONSIDERATIONS:
To obtain a detail report, with one line per monitor
interval, specify 0 for the Summarization Period in the
run-time execution parameters.
+----------------------------------------------------------------------------------------------------------------------------------+ | Detail VMX Demand Scan Summary | | CA I/S MANAGEMENT APPLICATIONS DEVELOPMENT | | | |INQUIRY: VMXTX4 RUN DATE: 15MARyy | | System ID = VM01 Date = Wednesday, February 10, yyyy | |----------------------------------------------------------------------------------------------------------------------------------| | DEMAND SCAN PASS 1 DEMAND SCAN PASS 2 DEMAND SCAN EMERGENCY PASS SCAN | | -------------------------------- ---------------------- --------------------------- NOT ALIST DEFRD | | TIME LTD STD SYS/SHAR ELST DLST LTD STD ELST DLST SYS/SHAR STD ELST DLST CMPL EMPTY TASKS | |----------------------------------------------------------------------------------------------------------------------------------| |12:25:00 14.0 0.0 0.0 0.0 3.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 56.0 | |12:30:00 28.4 0.0 0.0 0.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.0 80.0 | |12:35:00 54.7 0.0 0.7 0.0 7.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.3 149.3 | |12:40:00 79.5 0.0 0.0 0.0 9.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.5 288.0 | |12:45:00 89.0 0.0 0.5 0.0 9.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.5 264.0 | | | | | | | | | | | | | | | | | +----------------------------------------------------------------------------------------------------------------------------------+
Figure 3-5. Detail VMX Demand Scan Summary
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