The Range of Possible User Requirements for DW Archiving Sample Clauses

The Range of Possible User Requirements for DW Archiving. A first step in clarifying and simplifying the archiving problem, is to assert that the focus will be on preservation of the logical structure of the data warehouse, rather than any specialised physical storage structures that may have been used for performance enhancement at the time the DW was originally constructed. Aside from the accepted division between logical and physical database design, which has a long pedigree in the literature, justification for this approach also derives from the continued pace of technological development on the hardware side – today’s special purpose performance accelerator is matched by tomorrow’s general purpose hardware/software configuration (with faster cpu/disk throughput and larger available memory). A second, and possibly controversial (in some quarters) step, is to assert the greater generality of the Relational OLAP94 approach to DW, as compared to the more specialised and less used MOLAP95 or HOLAP96 94 A Relational OLAP implementation means that all the dimensions and fact tables are represented as tables, while the metadata that specifies the linkages between facts and dimensions, and the hierarchical structure (if any) of the dimensions themselves, is all stored in data dictionary views. The SQL query processor then uses the SQL OLAP extensions, together with the metadata, to create virtual OLAP cubes or subsets of cubes at query approaches. A particular reason for favouring the ROLAP approach in a DW archiving context is also that it will allow the use of tools already developed in E-ARK and other projects for archiving standard relational databases, thereby lessening the burden of required new development of concepts/tools specifically for DW archiving purposes. A possible corollary of going down the ROLAP only route is that older legacy MOLAP/HOLAP systems will need to provide the ability to move data into ROLAP-only structures. Further investigation will be needed to determine whether this is likely to prove a widespread impediment to effective archiving workflows in future, or whether its impact will be limited to isolated special cases where vendors have not already provided the requisite functionality. It should be noted that adopting ROLAP to the exclusion of other approaches also has (potentially beneficial) implications for the problem of archiving OLAP cubes. This will be discussed in more detail in a later section. The third basic xxxxx of the archiving approach to be adopted is that it will assume...