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

SEQUENCE_GENERATOR_CACHE_MAXIMUM
Runtime controlsCategory
Controls the maximum setting of the internal sequence generator cache size per request.
The cache is used to set how many unique values are obtained from the sequence generator
per request. The computation starts with the SEQUENCE_GENERATOR_CACHE_INITIAL,
then multiplies it with the SEQUENCE_GENERATOR_CACHE_INCREMENT and compares
it to the SEQUENCE_GENERATOR_CACHE_MAXIMUM. For example, if the defaults
for the CQDs were used, then SEQUENCE_GENERATOR_CACHE_INITIAL would provide
the initial value of “1”. A cache of “1” would be obtained. When the cache was exhausted,
“1” would be multiplied by the SEQUENCE_GENERATOR_CACHE_INCREMENT of
“10”, supplying a new cache of 10 numbers. This dynamic calculation continues to increment
the numbers from “1” to “10” to “100” to “1000” to “10000”. “10000” is the
SEQUENCE_GENERATOR_CACHE_MAXIMUM default, so no additional multiplication
would occur. The maximum would be used from that point on to determine the cache size.
The compiler calculates the optimal sequence generator cache maximum setting for an
insert query that obtains values for an identity column from an internal sequence generator.
Description
Value is greater than 1.Any unsigned integer
The default value is ‘10000’.
Values
The maximum value is the steady state number of sequence values that are retrieved from
the sequence generator object for long-running inserts/loads. So while the initial and
increment values certainly determine the number of more frequent accesses made to the
sequence generator object during the ramp-up, the maximum value influences the number
of accesses made for long-running jobs once the maximum value is reached.
Choosing a large number can reduce the number of accesses, but can also result in a large
number of unused values from the last set of inserts, resulting in large gaps in the identity
column values.
Usage
Not applicableProduction usage
The maximum value setting can influence the number of accesses made to the sequence
generator object to retrieve a set of values to be cached for use for identity columns. It can
also result in large gaps in identity column values.
Impact
Set this CQD at the system level. However, overriding the defaults may make sense at a
service level to influence certain loads/insert transactions, or even at a session level for
loads.
Level
Works in conjunction with the CQDs SEQUENCE_GENERATOR_CACHE_INITIAL and
SEQUENCE_GENERATOR_CACHE_INCREMENT, and cannot be considered in isolation.
The maximum value determines how many accesses are made to retrieve the set of values,
depending on the initial and increment settings.
Conflicts/Synergies
Not applicableAddressing the real
problem
Neoview Release 2.4Introduced in release
Not applicableDeprecated in release
40 Sequence Generator