Neoview Control Query Default (CQD) Reference Guide (R2.5)

15 Miscellaneous
This section describes these miscellaneous CQDs:
• “DEF_MAX_HISTORY_ROWS” (page 59)
• “LAST0_MODE” (page 59)
• “QUERY_LIMIT_SQL_PROCESS_CPU” (page 60)
• “STREAM_TIMEOUT” (page 61)
• “AUTO_QUERY_RETRY_WARNINGS” (page 61)
• “SAVE_DROPPED_TABLE_DDL” (page 62)
DEF_MAX_HISTORY_ROWS
Runtime controlsCategory
Controls the maximum number of rows maintained in the history buffer used for OLAP
Window functions and Sequence functions. In many cases, the maximum number of rows
needed for the history buffer can be determined by the expressions in the query. In these
cases, this computed maximum is used and the value of the control is ignored. However,
in cases when the maximum history rows required cannot be determined, the value of the
control is used.
Description
The value represents the number of rows maintained in the
history buffer used for OLAP Window functions and Sequence
functions.
Integer greater than
‘1024’
The default value is ‘1024’.
Values
Use this control default to adjust the size of the history buffer for queries which need more
than the default number of history rows. These are queries for which the maximum size
of the history buffer cannot be determined.
For OLAP window functions, these are queries which contain an OLAP Window function
which has a Partition Clause and which does not have a fixed Window size specified in
the Frame Clause. For OLAP Window functions, if the current setting of this query is too
small, the runtime returns the error [8840] "The size of the history buffer is too small to
execute one or more of the OLAP Windowed Functions in the query."
For Sequence functions, these are queries which contain a Sequence function with a variable
window size or offset. For Sequence functions, if the current setting of this query is too
small, the runtime returns a NULL value for the function.
Usage
Not applicableProduction usage
This control default can affect the number of history rows maintained in memory and so
can impact the amount of memory used by the query.
Impact
QueryLevel
Not applicableConflicts/Synergies
Not applicableAddressing the real
problem
Neoview Release 1.0Introduced in release
In R2.5, dynamic buffering and overflow is supported for OLAP Window functions. So for
OLAP Window functions, this control default is no longer necessary. However, it still
applies to Sequence functions.
Deprecated in release
LAST0_MODE
Runtime controlsCategory
Ensures that all parts of the query plan are executed but no rows are returned by the query.Description
DEF_MAX_HISTORY_ROWS 59