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

If the sample table is missing, the compiler creates the sample
table before using it to estimate cardinalities.
‘ON’
The sample table is used to estimate cardinalities if it exists, else
the optimizer continues to use histograms.
‘OFF’
The default value is ‘OFF’.
Values
The feature can be used to control the usage of Compile Time Statistics (CTS). A customer
can disable the use of CTS for a specific table in a query, irrespective of the predicates on
that table, by not creating the sample table for it.
If the customer does not want to spend the effort determining which tables to generate a
sample for, and the overall benefit of CTS far outweighs the initial compile time creation
of the sample table (that impacts only the first query that finds no sample table when it
needs it), this CQD can be set to ON to ensure CTS is always used regardless of whether
a sample table exists or not.
Usage
Not applicableProduction usage
Auto creation of the sample table can increase the compile time the first time it is needed.
The sample table is reused for subsequent compiles if needed.
Impact
AnyLevel
The CQD is effective only when HIST_USE_SAMPLE_FOR_CARDINALITY_ESTIMATION
is set to ON.
Conflicts/Synergies
Not applicableAddressing the real
problem
Neoview Release 2.5Introduced in release
Not applicableDeprecated in release
HIST_MISSING_STATS_WARNING_LEVEL
HistogramsCategory
Controls the level of missing statistics warnings that should be displayed. The warnings
impacted are 6007, 6008, 6010 and 6011.
Description
32 Managing Histograms