Quantum CDSC

The Quantum CDSC reads data from, and writes data to, a Quantum-format ASCII file. The Quantum CDSC is also used for reading and writing fixed format Triple-S data files.

The Quantum DSC has the following features:

Feature	Quantum Data File
Storage type	1 or 2 files
Read	Yes
Write/update	Yes1
Unbounded loops (levels)	No
Native WHERE clause support	No
Compressed format	No
Multiple user read	Yes
Multiple user write	No

1 The Quantum CDSC supports variable updates only in *.dat files. The CDSC does not support text variable updates in *.dau files.

Data is stored by the Quantum CDSC in a fixed format data file; text values are optionally stored in an overflow file. The *.dat data file is a Quantum-format ASCII, or a Triple-S fixed format, data file that stores question responses according to the custom properties that are defined in the associated metadata document.

For more information about the Quantum CDSC custom properties, see Card, column, and punch definitions and Custom properties created when reading from Triple-S files.

The Quantum CDSC overall storage file size (in MB) is as follows:

skidemo	UNICOM Intelligence database	UNICOM Intelligence file	Quantum	Quanvert	SPSS
Total size	19	2.18	0.9	3.25	1.7
Backup	18.1	0.65	*	2	*

Although the storage size for the Quantum CDSC is the smallest of the test data sets, the fixed width storage, based on variable instances, can be larger than other formats for sparsely populated data sets. For example, when a different test data set (that contains large, sparsely populated loops) is used, the Quantum CDSC *.dat file is 502 MB, compared to 152 MB for the DDF DSC.

The following table provides the Quantum CDSC read performance (measured in seconds):

skidemo	UNICOM Intelligence database	UNICOM Intelligence file	Quantum	Quanvert	SPSS
1 variable	0.062	0.062	0.109	0.031	0.062
5 variables	0.11	0.063	0.204	0.078	0.078
All variables	1.078	0.562	0.843	0.672	0.61

▪The Quantum CDSC has acceptable read performance for the entire data set, making it a good input data format for data management activities.

▪In comparison to some of the other DSCs, the Quantum CDSC exhibits poor single variable read performance, making it less suited for ad hoc tabulation.

The following table provides Quantum CDSC write performance (measured in records per second):

skidemo	UNICOM Intelligence database	UNICOM Intelligence file	Quantum	Quanvert	SPSS
Records per second	80	1897	1523	*	1971

The following table provides update performance (measured in seconds) for every value in a single weight column:

skidemo	UNICOM Intelligence database	UNICOM Intelligence file	Quantum	Quanvert	SPSS
1 variable	0.719	0.219	0.282	*	0.578

▪The Quantum CDSC has acceptable write and update performance, making it suited for data management operations, such as cleaning, coding, and weighting.

▪Because updates to an existing file is only supported for variables in the *.dat file, and that new variables cannot be added after the file is created, the Quantum CDSC must not be used for UNICOM Intelligence applications.

The recommended Quantum CDSC usage is as follows:

▪Data export to other formats. The Quantum CDSC has acceptable read performance for exporting to other DSCs.

▪Data management. Copying data to the Quantum CDSC is fast, and the CDSC provides acceptable update performance when updating weight or coding variables.

▪Tabulation. The Quantum CDSC has acceptable performance when used for large table runs that involve many variables.

▪Portable data format. The main purpose of the Quantum CDSC is to provide data import/export for either the Quantum or Triple-S formats. In particular, the Triple-S format is an excellent choice as a portable data format given that it is supported by other Market Research software applications.

The Quantum CDSC is not suited in the following scenarios:

▪Data collection. The Quantum CDSC cannot be used for data collection applications because it cannot update existing text values in the overflow file.

▪Ad hoc tabulation/analysis. The Quantum CDSC exhibits poor single variable read performance, making it less appropriate for ad hoc tabulation scenarios.

▪Unbounded levels data. The Quantum CDSC does not support unbounded loops and cannot be used to store levels data.

▪Updates to coding variables. Coding variable updates are often run with UPDATE statements with a WHERE clause. The statements indicate which respondent records must be updated. The Quantum CDSC does not support native WHERE clause evaluation, making it less suited for coding.

The following issues are known to impact Quantum CDSC performance:

▪Reading text variables in the *.dau overflow file. The Quantum CDSC does not read the *.dau file if a query does not reference any text variables. As a result, when a tabulation request does not reference text variables, and the *.dau file is large, the population time can be faster than when the tabulation request references text variables.

▪Large, sparsely populated data sets. For sparsely populated data sets, the fixed width storage that is used by the Quantum CDSC is larger and slower than other formats (that allocate storage only for actual responses).