Csci12 report aug18
- 1. GROUP 5 Master Jenniferson Napallatan Neri Openiano Ostil
- 2. TOPICS Index Indexed Sequential File Properties of Indexed Sequential File Datawarehousing
- 3. Index Indexes provide fast searching of a table based on one or more key columns. Indexes on foreign keys can also greatly improve the performance of join.
- 4. Indexed Sequential File A file combining properties of random-access files and sequential files
- 5. Records in indexed sequential files are stored in the order that they are written to the disk. Records may be retrieved in sequential order or in random order using a numeric index to represent the record number in file
- 6. Properties Primary Storage Area : Records in indexed sequential files are stored in the order that they are written to the disk. Records may be retrieved in sequential order or in random order using a numeric index to represent the record number in the file.
- 7. Properties Records are stored sequentially, originally to speed access on a tape system. In contrast, a relational database uses a query optimizer which automatically Selects indexes. The record size, specified when the file is created, may range from 1 to 8000 bytes.
- 8. Properties 2. Separate Indexes : The Indexed Access method of reading or writing data only provides the desired outcome if in fact the file is organized as an ISAM file with the appropriate, previously defined keys. Access to data via the previously defined key(s) is extremely fast.
- 9. Properties Multiple keys, overlapping keys and key compression within the hash tables are supported. A utility to define/redefine keys in existing files is provided. Records can be deleted, although "garbage collection" is done via a separate utility.
- 10. Properties 3. Overflow Area : When an ISAM file is created, index nodes are fixed, and their pointers do not change during inserts and deletes that occur later (only content of leaf nodes change afterwards).
- 11. Properties node exceed the node's capacity, new records are stored in overflow chains. If there are more inserts than deletions from a table, these overflow chains can gradually become very large, and this affects the time required for retrieval of a record.
- 12. Properties Indexed sequential files: commonly used for transaction files because they take less disk space than keyed files, and are faster to read from beginning to end than a keyed file.
- 13. Data Warehousing What is a Data Warehouse? DW is a subject-oriented , integrated , time-variant , and nonvolatile collection of data intended to support management decision making
- 14. Data Warehousing What is a Data Warehouse? DW is a subject-oriented , integrated , time-variant , and nonvolatile collection of data intended to support management decision making
- 15. Data Warehousing DATABASE vs DATA WAREHOUSE Database: transactional (relational, object-oriented, network, heierarchical) Data Warehouse: mainly INTENDED for decision support applications **optimized for retrieval not routine transactional processing**
- 16. Data Warehousing What is a Data Warehousing? combining multiple and usually varied sources into one comprehensive and easily manipulated database. (wiseGEEK.com)
- 17. Data Warehousing Properties: 1. Organized around major subject areas of an org. (i.e. sales ,suppliers,products, etc.) 2. Integrated from multiple operational OLTP data sources ** OLTP = OnLine Transaction Processing db
- 18. Data Warehousing Properties: 3. Periodic updates (based on schedules) There is a trend wherein updates are gearing towards near real-time reporting of business analytics.
- 19. Data Warehousing Advantages: Competitive advantage Increased productivity of corporate decision makers 3. Potential high return on investment as the org. Finds the best way to impove efficiency and/or profitability
- 20. Data Warehousing Encountered Problems: Underestimation of resources required to load the data 2. Hidden data integrity problems in source data 3. Omitting data later found to be required
- 21. Data Warehousing Encountered Problems: 4. Ever increasing end user demands 5. Consolidating data from diparate data sources 6. High resource demands (huge amount of storage; queries that process millions of rows) 7. Ownership of data
- 22. Data Warehousing Encountered Problems: 8. Difficulty in determining what the business really wants or needs to analyze 9. “Big Bang” projects that seem never-ending