[ Pobierz całość w formacie PDF ]
.The following listsummarizes the new terms:Parameters placed in the parameter file are used toinitializationparameters and specify configuration settings when starting anparameter filesinstance.In Version 6 documentation, initializationparameters were commonly referred to asINIT.ORA parameters.In Version 6 documentation, the file containinginitialization parameters was referred to as theINIT.ORA file.In Oracle7 documentation, it isknown as the parameter file.A schema is a logical space in which a user canschemacreate objects.In Version 6, there was no distinctionbetween a user and a collection of objects that theuser owns.In Oracle7, that distinction isintroduced with the term schema.Every user has one schema in which objects can becreated.The name of that schema is the same as theuser s Oracle username.Objects are uniquelyidentified by the schema to which the objectbelongs and the object name.For example, thetable EMP created in SCOTT s schema is identifiedas SCOTT.EMP.In Version 6, it was only necessary to talk aboutschema objectstables, views, and users.In Oracle7, there aretables, views, snapshots, roles, profiles, users,procedures, packages, triggers, and integrityconstraints, among other entities.These are knowncollectively as database objects.A process that handles requests (programserver processinterface calls) from user processes.A server processcan be either dedicated to one user process, orshared among many user processes, dependingon the configuration of your database system.In Version 6, these processes were known as shadow processes .Summary of Changes in Oracle7, Release 7.0 A 3 A logical connection by a user to the database.Onesessionuser can have several sessions.The Version 6 term user process has been replaced by user session in Oracle7.In Version 6, the parsed form of SQL statementsshared SQL areaswere stored in user context areas.In Oracle7, theyare stored in shared SQL areas.See page A 17 formore information.Functionality EnhancementsData verification can now occur within Oracle, as well as at theEnforced Integrityapplication level.By checking data at the application level, you canConstraintsensure that the users of a particular application receive immediateuseful and appropriate help and error messages when they access atable.Checking at the database level ensures that no incorrect data canbe entered in the table, regardless of which application or tool is used.Data checking at the database level is accomplished by usingintegrity constraints.Integrity constraints can be defined to specify logical relationships ofdata in a database.Version 6 introduced syntactic support for dataintegrity constraints.Oracle7 supports the enforcement of integrityconstraints to ensure that a database contains consistent data.If a DataManipulation Language statement violates an integrity constraint, thestatement is rolled back and an error is returned.Enabling Constraints Integrity constraints can be enabled or disabled.When constraints areenabled on existing data, an exception table can be generated to list allrows that violate constraints along with the constraints they violate.Unique Constraints In Version 6, the fact that table indexes were unique wasfrequently used to enforce uniqueness constraints.This is no longernecessary in Oracle7 since the UNIQUE constraint can now be used toguarantee uniqueness.Delete Cascade When deleting a master row that is referenced by foreign keys in othertables, you can choose to cascade the delete, dropping all foreign keyrows, as well as the master row.A 4 Oracle7 Server Migration Standards Compliance The integrity constraints implemented in the Oracle7 Server fullycomply with the SQL89 Level 2 standard set forth by ANSIX3.135 1989 and ISO 9075 1989.Along with Oracle7, the Release 1.5 precompiler is 100% compliantwith the ANSI SQL89 standard, including integrity features.In addition, the Release 1.5 precompiler passes 100% of the testscontained in the National Institute of Standards and Technology (NIST)SQL89 test suite.It also contains the FIPS Flagger (required by theFederal Information Processing Standard) to call attention to anynon ANSI standard extensions that are used.You can now specify a default value to be used for a column byEnforced Defaultsupplying an expression for the DEFAULT clause of the ALTER orValuesCREATE TABLE statement.If you issue an INSERT statement withoutproviding a column value, this default value will be used.Version 6introduced syntactic support for default values, whereas Oracle7supports the use of default values.National Language Support (NLS) in Oracle7 supports the use ofExtended Nationalmulti byte character sets used in many Asian languages.It alsoLanguage Supportprovides greater flexibility in specifying language or territory, either fora session or for the entire database.New NLS initialization parameters allow the specification of defaultdate format, currency symbol, number group separator, and decimalcharacter.These format characteristics can also be specified explicitly inSQL functions to override the default values.The values of all NLS parameters are defined with systemwidedefaults, and can be overridden on a per session basis.Differentsessions connected to the same instance can use different values forNLS parameters.These values can be changed during a session.For more information on NLS features supported by the Oracle7Server, see Oracle7 Server Concepts and Oracle7 Server Reference.The PL/SQL programming language now permits a stored procedure orPL/SQLfunction to be defined and compiled once, stored in the database, andthen executed by multiple users and applications.Stored proceduresand functions consist of a set of SQL and PL/SQL statements that arestored in a compiled form in the database.In addition, PL/SQL nowallows stored packages and database triggers.Summary of Changes in Oracle7, Release 7.0 A 5 Packages Packages provide a method of encapsulating and storing relatedprocedures, functions, cursors, variables, constants, and exceptionhandlers as a unit.Global package variables and constants can bedeclared and used by any procedure in the package.Between calls,variables and cursors retain their state for each session.Onlypublic data, procedures, and functions can be accessed from outsidethe package
[ Pobierz całość w formacie PDF ]