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# Glossary

Base Table

A source of data, either a table or a view, that underlies a view. When you access data in a view, you are really accessing data from its base tables.

Connected

Connected is a generic term that refers to users, applications, or devices that are connected to a server.

Database Object

A database object is a named database structure: a table, view, sequence, index, snapshot, or synonym.

Database Server

The database server is the third tier of the mobile server three-tier Web model. It stores the application data.

Disconnected

Disconnected is a generic term that refers to users, applications, or devices that are not connected to a server.

Foreign Key

A foreign key is a column or group of columns in one table or view whose values provide a reference to the rows in another table or view. A foreign key generally contains a value that matches a primary key value in another table. See also "Primary Key".

Index

An index is a database object that provides fast access to individual rows in a table. You create an index to accelerate queries and sorting operations performed against the table's data. Indexes can also be used to enforce certain constraints on tables, such as unique and primary key constraints.

Indexes, once created, are automatically maintained and used for data access by the database engine whenever possible.

Integrity Constraint

An integrity constraint is a rule that restricts the values that can be entered into one or more columns of a table.

JDBC

JDBC (Java Database Connectivity) is a standard set of Java classes providing vendor-independent access to relational data. Modeled on ODBC, the JDBC classes provide standard features such as simultaneous connections to several databases, transaction management, simple queries, manipulation of pre-compiled statements with bind variables, and calls to stored procedures. JDBC supports both static and dynamic SQL.

Join

A relationship established between keys (both primary and foreign) in two different tables or views. Joins are used to link tables that have been normalized to eliminate redundant data in a relational database. A common type of join links the primary key in one table to the foreign key in another table to establish a master-detail relationship. A join corresponds to a `WHERE` clause condition in an SQL statement.

Leapfrog Sequence

The leapfrog sequence is one of two sequence types that provides a unique primary key values to the mobile client. Leapfrog sequences contain a different start value for each client, and each sequence increment is set to a larger value than the maximum number of clients.

Master-Detail Relationship

A master-detail relationship exists between tables or views in a database when multiple rows in one table or view (the detail table or view) are associated with a single master row in another table or view (the master table or view).

Master and detail rows are normally joined by a primary key column in the master table or view that matches a foreign key column in the detail table or view.

When you change values for the primary key, the application should query a new set of detail records, so that values in the foreign key match values in the primary key. For example, if detail records in the `EMP` table are to be kept synchronized with master records in the `DEPT` table, the primary key in `DEPT` should be `DEPTNO`, and the foreign key in `EMP` should be `DEPTNO`. See also "Primary Key" and "Foreign Key".

MIME

MIME (Multipurpose Internet Mail Extensions) is a message format used on the Internet to describe the contents of a message. MIME is used by HTTP servers to describe the type of file being delivered.

MIME Type

MIME Type is a file format defined by Multipurpose Internet Mail Extension (MIME).

Mobile Development Kit

The Mobile Development Kit enables application developers to develop and debug applications.

Mobile Manager

The Mobile Manager is a mobile application that runs in the browser for easy administration of applications and users. administrators use the Mobile Manager to perform such functions as granting or revoking application access to users or groups, modifying snapshot template variables, or deleting applications from the mobile server.

Mobile Server Repository

The mobile server repository is a virtual file system that resides on Oracle. It is a persistent resource repository that contains all application files and definitions of the applications.

ODBC

ODBC (Open Database Connectivity) is a Microsoft standard that enables database access on different platforms. You can enable ODBC support on the mobile client for troubleshooting purposes. ODBC support enables you to view the client's data, which is stored on a local database.

Oracle Database

The Oracle database is the database component of the mobile server.

Oracle Database Mobile Server

The mobile server resides on the application server tier of the three-tier mobile server model and processes requests from mobile clients to modify data in the database server.

Packaging Wizard

The Packaging Wizard enables developers to define and package new or existing mobile server applications.

Positioned Delete

A positioned `DELETE` statement deletes the current row of the cursor. Its format is as follows:

    DELETE FROM table   WHERE CURRENT OF cursor_name

Positioned Update

A positioned `UPDATE` statement updates the current row of the cursor. Its format is as follows:

    UPDATE table SET set_list   WHERE CURRENT OF cursor_name

Primary Key

A table's primary key is a column or group of columns used to uniquely identify each row in the table. The primary key provides fast access to the table's records, and is frequently used as the basis of a join between two tables or views. Only one primary key may be defined per table.

To satisfy a `PRIMARY KEY` constraint, no primary key value can appear in more than one row of the table, and no column that is part of the primary key can contain a `NULL` value.

Referential Integrity

Referential integrity is defined as the accuracy of links between tables in a master-detail relationship that is maintained when records are added, modified, or deleted.

Carefully defined master-detail relationships promote referential integrity. Constraints in your database enforce referential integrity at the database (the server in a client/server environment).

The goal of referential integrity is to prevent the creation of an orphan record, which is a detail record that has no valid link to a master record. Rules that enforce referential integrity prevent the deletion or update of a master record, or the insertion or update of a detail record, that creates an orphan record.

Registry

The registry contains a unique name/value pairs. All registry names must be unique.

Replication

Replication is the process of copying and maintaining database objects in multiple databases that make up a distributed database system. Changes applied at one site are captured and stored locally before being forwarded and applied at each of the remote locations. Replication provides users with fast, local access to shared data, and protects the availability of applications because alternate data access options exist. Even if one site becomes unavailable, users can continue to query or even update the remaining locations.

Replication Conflict

Replication conflicts occur when contradictory changes to the same data are made. Replication conflicts can be avoided by proper subsetting of data. The Packaging Wizard allows the developer to specify rules on how to handle conflicts.

Schema

A schema is a named collection of database objects, including tables, views, indexes, and sequences.

Sequence

A sequence is a schema object that generates sequential numbers. After creating a sequence, you can use it to generate unique sequence numbers for transaction processing. These unique integers can include primary key values. If a transaction generates a sequence number, the sequence is incremented immediately whether you commit or roll back the transaction.

Sequence Window

The sequence window contains a unique range of values. The range of values never overlaps with those of other clients. When a client uses all the values in the range of its sequence window, the mobile client recreates the sequence with a new, unique range of values.

Snapshots

Snapshots are copies of application data that are captured in real-time from the Oracle database and downloads the same to the client. A snapshot can be a copy of an entire database table, or a subset of rows from the table. When you define your snapshot, you can use the `SQL` `WHERE` clause to specify a parameterized SQL query, where only the row data that your application uses is downloaded to the client. Thus, you can define what is downloaded to the client: the entire contents of the table or the subset of information that is relevant to the specific user. Most applications specify a particular subset of data that is relevant only to the user to be downloaded.

The snapshots are automatically created on the client machine. Each subsequent time that a user goes connects through synchronization, the snapshots are either refreshed with the most recent data, or recreated depending on the complexity of the snapshot.

SQL

SQL, or Structured Query Language, is a non-procedural database access language used by most relational database engines. Statements in SQL describe operations to be performed on sets of data. When a SQL statement is sent to a database, the database engine automatically generates a procedure to perform the specified tasks.

Synchronization

Synchronization is the process used to replicate data between the mobile client and Oracle. The mobile server replicates (downloads) the user applications and data to the mobile client from the repository, based upon the SQL query defined in the publication. In addition, all modifications made on the client are uploaded to the Oracle Server, if the publication is defined as updateable and not as read-only.

Synonym

A synonym is an alternative name, or alias, for a table, view, sequence, snapshot, or another synonym.

Table

A table is a database object that stores data that is organized into rows and columns. In a well designed database, each table stores information about a single topic (such as company employees or customer addresses).

Three-Tier Web Model

The three-tier Web model is an Internet database configuration that contains a client, a middle tier, and a database server.

Transaction

A set of changes made to selected data in a relational database. Transactions are usually executed with a SQL statement such as `ADD`, `UPDATE`, or `DELETE`. A transaction is complete when it is either committed (the changes are made permanent) or rolled back (the changes are discarded).

A transaction is frequently preceded by a query, which selects specific records from the database that you want to change. See also "SQL".

Unique Key

A table's unique key is a column or group of columns that are unique in each row of a table. To satisfy a `UNIQUE KEY` constraint, no unique key value can appear in more than one row of the table. However, unlike the `PRIMARY KEY` constraint, a unique key made up of a single column can contain `NULL` values.

View

A view is a customized presentation of data selected from one or more tables (or other views). A view is like a "virtual table" that allows you to relate and combine data from multiple tables (called base tables) and views. A view is a kind of "stored query" because you can specify selection criteria for the data that the view displays.

Views, like tables, are organized into rows and columns. However, views contain no data themselves. Views allow you to treat multiple tables or views as one database object.