Division Remainder Hashing Algorithm The general computation for determining a relative storage address slot for a particular record is: Relative slot address = 1 + Remainder of Primary Key Value _ Total Number of Reserved Address Slots Assume a PRODUCT file with 4, 500 unique records. The storage allocation for this file is equal to the number of records, therefore 4,500 storage slots will be needed on the media. The primary key for records in this file is the PRODUCT_ID field. The location for PRODUCT_ID 734171 can be computed as follows: Relative slot address = 1 + Remainder of 734171 _ = 1 + 671 = 672 4500
Object-Oriented Database Architecture Methods Object Class A Object Attributes Methods Object Class C Object Attributes Object Class B Object Attributes Methods
Common Data Type Definitions Data Type Description CHAR( n ) Alphanumeric character array with a maximum length of n. DECIMAL( m,n ) Signed numerical data with a total number of digits, m , and n number of digits to the right of the decimal point. VARCHAR Alphanumeric character array of variable length. INTEGER Signed whole number typically up to 11 digits in length SMALLINT Signed whole number up to 5 or 6 digits in length. DATE Date and time including appropriate validity checks (i.e. 4-31 not allowed). NUMBER Real number FLOAT( m,n ) Numerical data represented in scientific notation with a total number of digits, m , and n number of digits to the right of the decimal point. LOGICAL Binary data (i.e. TRUE/FALSE, YES/NO) LONG Variable length alphanumeric character array up to 2Gb LONGRAW Binary large object (BLOB) – no assumptions are made about format or content.
Common Field-Level Data Specifications Field Specification Description Field Name Formal name for the field that uniquely identifies it from all others. Data Type Data type associated with this field. Units The unit of measure associated with this field (if applicable). Maintenance Rules for update, change, or deletion once data is entered (i.e. accounting transaction data cannot be changed once entered). Missing Data Procedure for handling missing data during multiple record processing (i.e. IGNORE, USE AVERAGE OF OTHER RECORDS). Check Digit Algorithm for calculate and verifying any check digits used in this field. Formula Algorithm for computing the value of this field (if calculated). Coding Coding conventions or acceptable abbreviations (i.e. 2-character abbreviation for State). Domain/Range Specification of range limits or default values for the field. Referential Integrity Specification for any referential integrity constraints for the field. Data Owner Identification of the responsible party for identifying the source and meaning of data contained in this field.
Common Domain Controls Domain Control Description Default Value Automatic entry of a value commonly found for this field unless other data is entered. Range Control Imposition of acceptable or relevant limits on either alphanumeric or numerical data. Picture Control Imposition of a specific pattern for the data being entered (i.e. DATE= mm/dd/yy or dd-mm-yyyy) Null Value Control Specification of whether a value in a particular field is required or optional.
Examples of Referential Integrity Deletion Rules Deletion Rule Explanation NO RESTRICTION Any record in the file may be deleted without regard to any other record or file. DELETE:CASCADE A deletion of a record must be automatically followed by the deletion of any matching records in any related files. DELETE:RESTRICT A deletion of a record in a table must be disallowed until any matching records are deleted from any related files. DELETE:SET NULL A deletion of a record must be automatically followed by setting any matching keys in a related file to NULL.
Common File Types File Type Description Master File Contains records related to business data that is relatively permanent. Once a record is entered, it tends to remain indefinitely. Data values may change (i.e. CUSTOMERS, PRODUCTS, INVOICES, SUPPLIERS). Transaction File Contains records that describe business events which can occur on a day-to-day basis. Data tends to have a limited useful life and are usually moved to an archival file after a predetermined period. Document File Contains stored copies of historical data in document form such that the overhead associated with recreated or reprocessing the document is eliminated. Table Look-Up File Contains reference data used to validate field values and to maintain consistency throughout the database (INCOME TAX TABLES, POSTAL CODE TABLES). Audit File Contains records of updates to other files in the database in case production files are damaged and require reconstruction. Data can be used with records in archival files to recover or restore damaged files or lost data. Archive File Contains records that have been deleted from active transaction files but require retention for an indefinite period. Work File Contains records stored temporarily or records containing intermediate results in a calculation process. Work files are usually created when needed and deleted upon completion of the task.
Volumetric Analysis FIELD SIZE (bytes) Invoice_ID 7 Invoice_Date 8 Customer_ID 6 Product_ID 9 Quantity 3 Unit_Price 6 Salesman_ID 4 Record Size 43 Record Overhead 25% Total Record Size 53.75 Total Annual Record Volume 67,000 Expected Table Volume 3,601,250 Expected Annual Growth Rate 16% Projected Table Volume – 4 years 5,621,176