Sybase 12.5.1, User Manual

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Control file
92
Historical Server
• The session ID of the session whose control information was most recently
written to the control file
• The number of session entries in the control file that are no longer valid
because one or more data files or error message files they refer to were
deleted
Following this header record are a number of records of different types that
describe all of the recording sessions, past and present, known to Historical
Server. These records appear in hierarchical sequential order in the control file,
where the hierarchy of record types in top-down order is:
• Session control
• View control
• Data item control
• Alarm control and filter control
For example, a session that consisted of two views, each with two data items
that had one alarm and one filter apiece, would be represented by the following
hierarchy of control records, stored in the following order:
session 1
view 1
data item 1
alarm 1
filter 1
data item 2
alarm 2
filter 2
view 2
data item 3
alarm 3
filter 3
data item 4
alarm 4
filter 4
The contents of the various control record types are described in the next
sections.
Session control record
The session control record contains: