SQL/MX 2.x Reference Manual (H06.10+, J06.03+)

Metadata Tables
HP NonStop SQL/MX Reference Manual—544517-008
10-58
Query Optimization and Performance
CHECK_CONSTRAINT_PRUNING Set to ON, OFF, RESET, or SYSTEM. The default is
ON. If OFF, the constraint based query pruning
optimization will not be tried on the subsequent
queries. The CQD value RESET or SYSTEM sets
the value of CQD back to the default value. The
constraint based pruning uses the Constant Range
Predicate Folding (CRPF) feature. The CRPF uses
EncodedValue objects to store the actual values as
double datatype with up to 15 digit of precision. For
datatypes that have precision more than 15 digits
(such as largeint), this conversion of actual value
from more precision to double, causes
comparisons to go wrong.Hence,constraint pruning
is not applied when the value for comparison
happens to have more than 15 digit of precision.
For information on check constraint pruning feature,
see the SQL/MX Query Guide.
CROSS_PRODUCT_CONTROL Set to ON or OFF. ON reduces compile time by
eliminating query plans that include unnecessary
and expensive cross-products (joins without join
predicates).
For additional information about this setting, see the
SQL/MX Query Guide.
The default is ON.
DATA_FLOW_OPTIMIZATION Set to ON or OFF. Reduces compile time by not
considering some query plans that have relatively
high data flow rates.
The default is ON, resulting in improvement in
compile time without impacting plan quality.
DP2_CACHE_4096_BLOCKS Specifies the number of 4 KB blocks allocated for
the disk cache. This value is used by the compiler to
determine the cost of a table/index scan operator.
You should set the value of this attribute to the
average value of 4 KB block disk cache settings for
all volumes in the system. The current value for the
number of 4 KB blocks allocated to a disk cache can
be determined by using SCF. See the SCF
Reference Manual for G-Series RVUs for details on
that product.
Allowed values: 1 through 1,4294967295.
The default is 1024.
FFDC_DIALOUTS_FOR_MXCMP Set to ON or OFF. Controls whether FFDC dial-outs
should occur when the compiler terminates
abnormally or detects an internal error.
The default is OFF, disallowing dial-outs.
Attribute Setting