Class DBMS

java.lang.Object

DBMS

public class DBMS
extends Object

The main class of a simple relational database. It includes the main() method, and methods for performing tasks or obtaining state involving the DBMS application as a whole (e.g., initialization, configuring the environment, aborting the application, etc.) To allow access to the DBMS methods from all other classes, we make all methods static, so that the class name can be used to invoke them. To run the application, enter the command

java DBMS

from the command line.

Field Summary

Fields

Modifier and Type	Field and Description
static String	DB_HOME The home directory of the BDB environment.
static boolean	DEBUG Set this to true to print debugging messages, and false to omit them.

Constructor Summary

Constructors

Constructor and Description
DBMS()

Method Summary

Modifier and Type	Method and Description
static void	abort() Attempts to immediately shut down the database and exit.
static Environment	getEnv() Returns the handle for the underlying BDB environment.
static void	init() Initializes the DBMS -- initializing the underlying BDB environment, the catalog, and the in-memory cache of open tables.
static void	main(String[] args) The main method for the DBMS application.
static void	shutdown() Prepares the DBMS to shutdown -- closing all open tables, as well as the catalog and the underlying BDB environment.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEBUG

public static final boolean DEBUG

Set this to true to print debugging messages, and false to omit them.

See Also:

Constant Field Values

DB_HOME

public static final String DB_HOME

The home directory of the BDB environment.

See Also:

Constant Field Values

Constructor Detail

DBMS

public DBMS()

Method Detail

main

public static void main(String[] args)
                 throws IOException

The main method for the DBMS application.

Throws:

IOException

init

public static void init()

Initializes the DBMS -- initializing the underlying BDB environment, the catalog, and the in-memory cache of open tables.

shutdown

public static void shutdown()
                     throws DatabaseException

Prepares the DBMS to shutdown -- closing all open tables, as well as the catalog and the underlying BDB environment.

Throws:

DatabaseException - if Berkeley DB encounters a problem when aborting transactions, closing the per-table databases, or closing the catalog database

abort

public static void abort()

Attempts to immediately shut down the database and exit. This method tries to abort all transactions and close all Berkeley DB databases using DBMS.shutdown(). If DBMS.shutdown() fails, an error message is printed. In all cases, the program exits.

getEnv

public static Environment getEnv()

Returns the handle for the underlying BDB environment.

Returns:

the environment handle