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

Not applicableAddressing the real
problem
Neoview Release 2.4Introduced in release
Not applicableDeprecated in release
SEQUENCE_GENERATOR_CACHE_INCREMENT
Runtime controlsCategory
Controls the incremental setting of the internal sequence generator cache size per request.
The cache size 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.
Description
Value is greater than 1.Any unsigned integer
The default value is ‘10’.
Values
The sequence generator increment setting is used as a multiplier to increase the number
of values being retrieved for each subsequent request for more values, until the maximum
is reached.
Using a small multiplier results in smaller step increases towards the maximum, and
therefore more trips to the sequence generator object for values. If the inserts to be done
are exhausted before reaching the maximum, this may lead to less wastage of retrieved
sequence values, and smaller gaps in identity column values. Using a higher multiplier
results in a faster ramp-up resulting in fewer trips to the sequence generator object for more
values, with the potential of more gaps in identity column values.
Based on the values of SEQUENCE_GENERATOR_CACHE_INITIAL and
SEQUENCE_GENERATOR_CACHE_MAXIMUM you can determine the number of trips
it takes, and the values fetched at each trip, depending on the increment value you choose
for this CQD. You can choose an increment that achieves the right balance between I/O to
retrieve values versus potential size of gaps in the identity column.
Usage
Not applicableProduction usage
As described in usage, this setting influences the trade off between trips (I/O) to the sequence
generator object to get more values versus the potential of unused values, or the size of the
gaps in the identity column values. Of course, the impact is only through the ramp up from
the initial value to the maximum value. Once the maximum value is reached, the number
of values retrieved is the same every time, and so is the frequency.
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_MAXIMUM, and cannot be considered in isolation.
The influence of the increment is based on the initial and maximum values.
Conflicts/Synergies
Not applicableAddressing the real
problem
Neoview Release 2.4Introduced in release
Not applicableDeprecated in release
38 Sequence Generator