5. FILES › 5.2 HAR Information Area Files › 5.2.16 Cache Volume Activity File (HARCVA) › 5.2.16.3 Usage Considerations

5.2.16.3 Usage Considerations

Special considerations or techniques related to using the
HARCVA file are provided below.

1.  RMF interval data represented in CA MICS database files
    uses time and duration information common to all RMF
    records for a given SYSID to ensure timestamp consistency
    across different CA MICS database files.

    This consistency allows CA MICS database records from
    different files (such as the HARCPU and HARDVA) to be
    merged together by ENDTS.

    The HARCVA file maintains this consistency.  Data element
    values for STARTTS, ENDTS, HOUR, DAY, INTERVAL, and so on
    are completely synchronized with the same element values
    found in other CA MICS database files generated from RMF
    data produced for the same time interval.  This not only
    aids in the merging of data, but also allows for strict
    minute cut-offs to ensure that data from 9:00-9:59 is
    always summarized into hour 9.

2.  The data in the HARCVA file may not actually represent
    activity exactly bounded by STARTTS and ENDTS.  This is
    because the actual reporting of cache statistics can be
    delayed by device reserve activity.  A unique set of
    Start Time, End Time, and Duration elements are provided
    with the HARCVA file. They represent the true time bounds
    of the data represented.  These elements are listed
    below:

    CACHESTS - Cache Gatherer Start Time Stamp
    CACHEETS - Cache Gatherer End Time Stamp
    CACHEDUR - Cache Gatherer Interval Duration
    CVAACTTM - Caching Active Time
    CVAIACTM - Caching Inactive Time

    All HARCVA observations contain a value in CACHESTS,
    CACHEETS, and CACHEDUR.  For intervals where caching was
    active, CVAACTTM is set equal to CACHEDUR.  When
    inactive or pending inactive, CVAIACTM is set equal to
    CACHEDUR.  This means that in higher timespans, such as
    MONTHS, the observation for VOLSER "VOL001" will contain
    the total cache activity duration (CACHEDUR) as well as
    the total time caching was active (CVAACTTM) and inactive
    (CVAIACTM).  The sum of CVAACTTM and CVAIACTM will always
    equal CACHEDUR.  These durations, rather than the RMF
    Interval Duration (DURATION) are used in all per-second
    rate calculations.

3.  DETAIL timespan HARCVA observations represent the
    caching activity for a single volume.  When bit settings
    in the raw RMF record indicate that caching was active at
    the end of the RMF interval, one set of CA MICS data
    elements is populated.  When caching was inactive or
    pending deactivation, another smaller set of data
    elements is populated.  This separation of I/O activity
    into two sets of mutually exclusive data elements allows
    the summarization of observations that include both cache
    active and inactive intervals into a single summarized
    observation while preserving the validity of I/O rate and
    cache hit ratio analysis.

    The following data elements are populated only when
    caching was inactive or pending deactivation at the end
    of the RMF interval:

    CVAIACTM - Caching Inactive Time
    CVAOFFIO - Total Cache Offline I/O
    CVAOFFR  - Total Cache Offline Read I/O
    CVAOFFW  - Total Cache Offline Write I/O
    CVAOFFO  - Total Cache Offline Other I/O

4.  Care must be exercised in using the special date and time
    data elements contained in each CA MICS file. As the
    file's granularity increases in higher timespans, certain
    fields lose significance; they should not be used in
    those cases.

    o  HOUR should not be used in MONTHS.
    o  DAY and DAYNAME should not be used in WEEKS, MONTHS.
    o  WEEK should not be used in MONTHS.

5.  ENDTS and STARTTS, when appearing in the DAYS, WEEKS, or
    MONTHS timespans, bound the span of time over which the
    data has been summarized.  STARTTS is the lowest date and
    time and ENDTS is the highest date and time for the data
    summarized.  These data elements have different meanings
    when used in the DETAIL timespan versus the DAYS, WEEKS,
    and MONTHS timespans.  Their purpose in DETAIL is
    described below:

    o  STARTTS represents RMF recording interval start time.
    o  ENDTS represents RMF recording interval end time.

    Remember that in the HARCVA file CACHESTS (Cache Gatherer
    Start Time Stamp) and CACHEETS (Cache Gatherer End Time
    Stamp) represent the true time boundaries of the data,
    and may be slightly different from the boundaries of the
    RMF interval duration.