Cloudscape Glossary,
Page 1 of 1


[top]
[prev]
[next]

Road Map
Glossary
Index for This Book
Documentation Top
Global Index

Cloudscape Glossary

ACID
The four properties of transaction control: Atomicity, Consistency, Isolation, and Durability.
Agreement
A situation in which the only difference between the corresponding data in two databases is latency. See Latency.
Applet
A Java program that is executed by a browser, as opposed to a stand-alone Java application.
Atomicity
The A in ACID. The property of transaction control that means that either all or none of the statements in a transaction are executed.
Auto-commit mode
A state within a JDBC application that means each individual SQL statement is treated as a transaction and is automatically committed when executed. To group two or more statements into a transaction, you must turn off auto-commit mode in the application, then explicitly commit a transaction. In a Cloudscape application, auto-commit causes cursors to close.
Backing index
An index that Cloudscape creates to enforce a primary key, unique, or foreign key constraint. So called because the index helps “back up” the constraint. Indexes created in this way are no different from indexes that you create with explicit CREATE INDEX commands, except that they have system-generated names.
Bulk import
Populating a table by importing data from a flat file instead of through insert statements.
Bulk export
Exporting the contents of an entire table or any subset of data in a database to a flat file using a Cloudscape-provided utility.
Check constraint
A boolean test applied to each row of a table on an insert or update to validate it.
Client/server environment
When multiple applications connect to Cloudscape over the network, they are said to run in a client/server environment. Cloudscape runs embedded in a server framework that allows multiple network connections. (The server framework itself starts up an instance of Cloudscape and, strictly speaking, it is running in an embedded environment; the client applications, however, are not.)
Class path
A list of directories or zip files to search for class files.
Commit
An operation that completes a transaction and causes all updates made during the transaction to be permanently written into a database.
Concurrency
Multiple users or programs simultaneously sharing the same database. Transactions and data locks are used to give each of these a consistent view of the database.
Conflict
In Cloudscape synchronization, a change submitted by a target database that, if allowed to apply at the source, would corrupt the data.
Conglomerate
A unit of storage within a Cloudscape database, either a table or an index.
Connection
A session with a database opened by a JDBC application program. Only one transaction at a time can be associated with a connection.
Consistency
The C in ACID. Consistency means that each transaction starts in a consistent state and ends in a consistent state. One transaction cannot “see” the changes caused by another transaction until that other transaction completes.
Constraint
In a database, a rule that ensures the integrity of data. Constraints can apply to columns or tables. An example of a -column-level constraint is that the values it contains must be unique.
Cursor
A construct used to reference the current position in a result. SQL defines a cursor mechanism that can be used through JDBC to do positioned updates and deletes.
Database
A Cloudscape database stores data as SQL-92 data types and Java objects. A Cloudscape database contains dictionary objects that organize the data. Cloudscape databases are stored in files in folders named after the database.
Database-side method
A Java method invoked in SQL-J and executed by Cloudscape.
Database-side JDBC method
A Database-side method that executes SQL-J statements, usually using a nested connection.
Database class loading
When you store application logic (in the form of jar files) in a database, you can configure Cloudscape (and your application) to load classes from the database instead of from the user’s class path.
Database connection URL
In JDBC, a URL that you specify as an argument to the -DriverManager.getConnection method call and that returns a connection to a database. Cloudscape’s database connection URL allows you to specify attributes to the connection.
DBMS
Database management system. Software that manages databases. Cloudscape is a DBMS, and it can run as an embedded database system under the same JVM as the database application program, or it can run as a database server, under a different JVM, or even on a different machine from that of the application.
DDL
Data Definition Language. A subset of SQL commands that create dictionary objects.
Dependency
The relationships among prepared statements and dictionary objects in a database. Cloudscape tracks the dependency that publications, stored prepared statements, and prepared statements have on the dictionary objects they access. If dropping or modifying a dictionary object would cause an open prepared statement to be invalidated, the change is not permitted.
Dictionary object
A user-defined entity contained in a Cloudscape database. When creating a database, users create and name dictionary objects such as tables, indexes, constraints, views, and stored prepared statements. Information about these dictionary objects is stored in the Cloudscape system tables, sometimes called the data dictionary.
Disk encryption
Encrypting a Cloudscape database, which is otherwise stored as clear text. You must specify a boot password when you boot the database in order to connect to it.
Durability
The D in ACID. Durability means that a transaction’s committed updates must be durable, even in the case of hardware or software failure.
Durable transaction
In Cloudscape synchronization, a transaction that has committed at the source.
Dynamic parameter
A parameter to a PreparedStatement whose value is unspecified when the statement is prepared. A dynamic parameter is represented by a question mark (?) in the SQL-J language.
Embedded environment
When an application starts up an instance of Cloudscape within its JVM, the application is said to run in an embedded environment. In this environment, only a single application can connect to a database at one time, and no network access occurs. The end-user may not even be aware of the database.
Environment
The way your application interacts with Cloudscape. Sometimes referred to as a framework. The two environments are Embedded environment and Client/server environment.
External virtual table
A virtual table in a FROM clause of an SQL-J statement in which a constructor of a class that fulfills Cloudscape’s Virtual Table Interface (VTI) requirements makes external data available to a SELECT statement.
Field access
In Cloudscape, accessing the static field of a Java class, or accessing the static or non-static field of an instance of a class. The class does not need to be serializable or stored in the database.
Hash join
A join operation in which Cloudscape uses a hash table for performance reasons. It is suitable for joins in which the outer table’s values are joined with single rows in the inner table, and values in the inner table are unique. See Nested loop join for comparison.
Index
A dictionary object that helps the DBMS find rows of a table quickly based on the values of one or more columns.
Inner table
In a join operation, a table that is not the outermost table. See Outer table for more information.
Isolation
The I in ACID. Isolation means that the database must give each connection data that appear to be unaffected by other transactions until the transaction commits.
Java data type
A Java class used within a Cloudscape system for storing instances in a table or for method invocation, or both. Also known as a user-defined data type. The class must be available to the Cloudscape system.
Java stored procedure
You may hear from other vendors about stored procedures written in Java that are declared with a statement such as CREATE PROCEDURE. These stored procedures are called Java stored procedures. In Cloudscape, you can call any Java method without having to declare it. In this documentation, we call such methods database-side methods, because you have the DBMS execute them. Such methods do not have to be stored in the database.
JDBC
The java.sql package, which is a set of classes and interfaces that make it possible to access databases from a Java application. (JDBC is not an acronym.)
JDBC driver
A Java class that implements the JDBC driver interface and is loaded into the JDBC driver manager. The core Cloudscape product comes with a built-in, local JDBC driver.
JDBC method
A method in a Java class that uses JDBC calls to access data in a Cloudscape database. When invoked from within Cloudscape, the method is called a database-side JDBC method.
JDK
Java Development Kit. The software released by JavaSoft to support the Java environments. The JDK includes the Java compiler and interpreter and many Java libraries.
JIT
Just-in-Time compiler. An alternative to a JVM; instead of interpreting byte code, it compiles it into machine code on the fly.
Join
The basic relational operator that allows data from more than one table to be combined.
JRE
Java Runtime Environment. Consists of the Java virtual machine, the Java platform core classes, and supporting files. It is the runtime part of the Java Development Kit—no compiler, no debugger, no tools. The JRE is the smallest set of executables and files that constitute the standard Java platform. A JRE is a JVM targeted primarily for developers who will be bundling the JRE with their applications for deployment.
JVM (Java Virtual Machine)
The program that interprets the byte codes of a Java application. A JVM is part of a JDK.
Keyword
A word that is part of a DBMS’s command vocabulary. The SQL-92 standard has defined a large number of keywords. Some are reserved, which means that they cannot be used for another purpose within an SQL statement unless delimited, and some aren’t. Cloudscape has its own additional keywords.
Latency
In a synchronized system, the time between a change at one database and the corresponding change at another database.
LDAP
Lightweight Directory Access Protocol. It provides an open directory access protocol running over TCP/IP. You can configure Cloudscape to authenticate users through an LDAP Directory Server.
Leaf level
The bottom level of a BTREE index.
Long row
A row that spans more than one database page. Cloudscape automatically overflows long rows that do not fit on a single database page.
LUCID
Logic up, consistent information down. This acronym describes Cloudscape’s synchronization model.
Metadata
Information about a database or a DBMS. Examples: the kind of functionality a DBMS provides, the types of data in the database, or information about a result set. In JDBC, you call the methods of the DatabaseMetaData or the ResultSetMetaData class to get this information.
Method
A procedure associated with a class or interface that defines one of the legal operations on instances of the class or interface. In Cloudscape, you can invoke methods that belong to a class stored in the database or to any class visible to Cloudscape.
Method Invocation
In Cloudscape, invoking a Java class method. The method can be either static or not static.
Nested connection
The “current” connection “re-used” by a database-side JDBC method. Such methods re-use the current connection so that statements that they execute are contained by a single transaction.
Nested loop join
The typical way that Cloudscape executes joins. Cloudscape loops through the inner table using the best access method available (usually an index) for every qualifying row in the outer table.
Null
A data value that is unknown or unspecified. Java has a distinguished null object value, and SQL has a distinguished null value that represents the absence of an actual value.
Object
An instance of a Java class. An object can be stored in a Cloudscape database if it implements the java.io.Serializable interface.
Optimization
A process in which the DBMS makes the best (optimal) choice of access paths and join order. True query optimization means that the DBMS will usually make the best choice independent of how the query is written. Cloudscape’s optimizer usually makes a good decision; you may sometimes want to override it.
Orderable Java data type
asdfasdf xxxxx
Outer table
In a join operation, the table that Cloudscape looks at first. It is best if the outer table is the one for which the fewest rows qualify, since Cloudscape will look up values in an inner table or tables for every qualifying row in the outer table.
Package
In a Java library of classes, a group of classes and interfaces. Package names are separated by dots and stored in directories that match these names. When specifying Java classes within an SQL-J statement, you must specify the package name along with the class name.
Page
A user-configurable unit of storage within a conglomerate. Conglomerates are made up of multiple pages.
Positioned update/delete
A mechanism to update or delete the row at the current position through an SQL cursor.
Prepared statement
An SQL statement that has been compiled for efficiency. The SQL processor parses and analyzes the statement and produces an execution plan for the prepared statement.
Primary key
The columns in a table that uniquely identify the rows in the table.
Property
In the Java world, a configuration parameter. You can set properties for Cloudscape systems, databases, queries, or single conglomerates.
Provisional transaction
In Cloudscape synchronization, a transaction that has committed at a target but has not yet committed at the source.
Publication
In Cloudscape synchronization, a dictionary object in a source database that defines a set of target databases. Source databases have publications; target databases subscribe to publications.
Pure Java
Refers to a program written entirely in Java. The tag “100% Pure” carries additional restrictions.
Query
The basic part of a SELECT statement.
RDBMS
Relational database management system. A DBMS that supports the SQL standard is considered relational.
Refresh
In a Cloudscape synchronization, a request issued by a target database to submit changes to the source and copy source changes to the target. All synchronization in Cloudscape is done using the refresh operation.
Result set
The rows that satisfy the conditions of a query. Cloudscape returns these rows through the JDBC interface in a JDBC ResultSet object. You can access the result set one row at a time.
Rollback
Undoing the changes made by a transaction before it commits. You can initiate a rollback by explicitly calling the JDBC Connection method rollback.
Row-Level locking
A locking system in which Cloudscape locks only rows, not entire tables. Row-level locking allows greater concurrency. Cloudscape uses locking to present data in a consistent state to multiple users or applications.
Schema
(1) A description of the dictionary objects in a database and their attributes.
(2) A database entity that consists of one or more tables, views, triggers, and so on. A schema provides a way to group a subset of tables within a database. A schema name qualifies a table name within a database.
Serialization
A Java mechanism for writing objects to an output stream. Cloudscape uses the serialization mechanism to store objects in a database.
Server
A machine that provides services of some kind to client machines on the network. A database server is a DBMS that provides services to applications that reside on client machines on the network. Cloudscape can be deployed as a database server by using Cloudconnector or another server framework.
Server framework
An application that enables multiple connections to Cloudscape. Unless Cloudscape runs inside a server framework, only one application at a time can access a Cloudscape database. Cloudconnector and RmiJdbc are server frameworks.
Source
In a Cloudscape synchronization system, the database from which data are copied to other databases (called targets).
SQL
A standardized database language for specifying queries and updates to databases. (At one time, SQL stood for Structured Query Language; now it’s another one of those acronyms, like JDBC, that do not stand for anything.)
SQL-J
Cloudscape’s Java-extended dialect of SQL-92.
SQL-92
The version of SQL standardized by ANSI and ISO in 1992.
SQL-92 entry-level
A subset of full SQL-92 specified by ANSI/ISO that is supported by nearly all major DBMSs today. JDBC compliance requires entry-level SQL compliance and defines escape syntax and metadata routines for more advanced features.
SQLExceptions
Errors generated during database access.
SQLState
Standard error code, defined by SQL-92, associated with SQLExceptions.
SSL
Secure Socket Layer. A protocol standard in wide use today for negotiating a secure connection.
Static method
A method that is associated with a class rather than an instance of the class.
Stored procedure
In some DBMSs, procedural code, written in SQL, executed by the DBMS. In Cloudscape, you execute Java methods instead of stored procedures.
Stored prepared statement
SQL-J statements named by the user and stored in a precompiled state for performance reasons.
Streaming column
Data stored via an input stream or retrieved via an output stream.
Synchronization
An operation that keeps distributed databases in agreement.
System
Semi-persistent environment for a Cloudscape session. Also a location; the default location for Cloudscape databases and configuration properties.
Target
In a Cloudscape synchronization system, a database created from a publication. See Publication.
Tear-Off Database
A target database.
Transaction
A sequence of JDBC/SQL calls within a single connection that constitute an atomic unit of work, that provide atomicity, consistency, integrity of data, and durability of database changes. In Cloudscape, transactions are handled entirely by JDBC calls.
URL
Uniform resource locator. First used on the WWW to identify HTML documents. A specialized form of URL is used by JDBC to identify databases. See Database connection URL.
User-defined data type
See Java data type.
Virtual Table Interface (VTI)
A Cloudscape construct that provides an interface to external data within an SQL-J statement. Classes that fulfill the VTI requirements can be used in the FROM clause to provide data to a SELECT statement. Cloudscape’s bulk import utility, COM.cloudscape.vti.FileImport, is an example of such a class.
WHERE clause
The portion of an SQL statement that allows the statement to retrieve a subset of rows that meet a particular set of conditions. Retrieving a subset of rows is sometimes called restriction. The WHERE clause requires a search condition (one or more predicates combined with AND, OR, and NOT) to specify the conditions under which you want rows to be chosen for inclusion in your set of data.
In a Cloudscape synchronization system, a table in a publication can include a WHERE clause.
Work unit
Two static Java methods, one at the target and one at the source, that perform a single logical operation and are referred to by a single alias.
[top]
[prev]
[next]


Cloudscape Version 3.0
For technical support, go to: www.cloudscape.com and click Support.
Copyright © 1998 and 1999 Cloudscape, Inc. All rights reserved.