Sybase 12.5.1, Руководство пользователя

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hs_playback_sample
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Historical Server
• Summary playback views do not require the server process to exist for
the duration of the playback sample. Summary views return rows for
all server processes included in any of the input views. However,
since Process ID is not guaranteed to be unique, the Kernel Process
ID must be included in any summary view that includes Process ID to
ensure uniqueness of the key. Otherwise, the summary could
erroneously combine data from two different processes.
Gaps in data within the playback session
The start_time and end_time parameters to the
hs_create_playback_session
command define the period of time that the
playback session covers. When the target parameter to the
hs_create_playback_session
command is
client
, there might be intervals of
time between the playback session’s start and end times for which no data
is available in any of the input sessions.
Note When target is
file
, no gaps are allowed in the specified input
sessions, so there will not be gaps in the playback session.
Gaps in available data might occur when:
• The input sessions specified for the playback session are not
contiguous. For example, if a series of input sessions covered the time
period between 9 a.m. and 5 a.m., Monday through Friday, data gaps
would exist between 5 p.m. each evening and 9 a.m. the next morning.
Larger gaps would exist between Friday evening and Monday
morning.
• The playback session does summarization and has a start or end time
beyond when data is available from the input sessions.
When the target of playback is a client, Historical Server handles gaps
according to the value of the missing_data_option parameter to the
hs_create_playback_session
command:
•
skip
(the default) – when a time period contains no data, the
hs_playback_sample
command goes directly to the next time period
containing data, rather than returning a sample having no data.
•
show
– the
hs_playback_sample
command returns a sample even for a
time period where no data is available. No data is returned (the length
of each data table returned is zero).