Archive | January, 2014


31 Jan








31 Jan

db i nmomory  how close it

H2 In-memory – The complete in-memory usage, keeps the complete database in main memory.  As soon as the database is shut down all the data gets lost.To use database in this way we neither need to explicitly start not stop it. Database will automatically become available as soon as you try to access it with specific URL.

In-memory jdbc url - jdbc:h2:mem:test;DB_CLOSE_DELAY=-1

Using the database in embedded mode Sample-
While including H2 in our application, we implemented facade for performing H2 related interactions and operations.


Unit test JPA Entities with in-memory database

31 Jan


31 Jan

guide sql
from the guide :

Closing the Database

All databases running in different modes can be closed with the SHUTDOWN command, issued as an SQL statement.

When SHUTDOWN is issued, all active transactions are rolled back. The catalog files are then saved in a form that can be opened quickly the next time the catalog is opened.

A special form of closing the database is via the SHUTDOWN COMPACT command. This command rewrites the .data file that contains the information stored in CACHED tables and compacts it to its minimum size. This command should be issued periodically, especially when lots of inserts, updates or deletes have been performed on the cached tables. Changes to the structure of the database, such as dropping or modifying populated CACHED tables or indexes also create large amounts of unused file space that can be reclaimed using this command.

Databases are not closed when the last connection to the database is explicitly closed via JDBC. A connection property, shutdown=true, can be specified on the first connection to the database (the connection that opens the database) to force a shutdown when the last connection closes.

Example 1.4. specifying a connection property to shutdown the database when the last connection is closed

 Connection c = DriverManager.getConnection(
         "jdbc:hsqldb:file:/opt/db/testdb;shutdown=true", "SA", "");

This feature is useful for running tests, where it may not be practical to shutdown the database after each test. But it is not recommended for application programs.

Creating a New Database

When a server instance is started, or when a connection is made to an in-process database, a new, empty database is created if no database exists at the given path.

With HyperSQL 2.0 the username and password that are specified for the connection are used for the new database. Both the username and password are case-sensitive. (The exception is the default SA user, which is not case-sensitive). If no username or password is specified, the default SA user and an empty password are used.

This feature has a side effect that can confuse new users. If a mistake is made in specifying the path for connecting to an existing database, a connection is nevertheless established to a new database. For troubleshooting purposes, you can specify a connection property ifexists=true to allow connection to an existing database only and avoid creating a new database. In this case, if the database does not exist, the getConnection() method will throw an exception.

Example 1.5. specifying a connection property to disallow creating a new database

 Connection c = DriverManager.getConnection(
         "jdbc:hsqldb:file:/opt/db/testdb;ifexists=true", "SA", "");

A database has many optional properties, described in the System Management chapter. You can specify most of these properties on the URL or in the connection properties for the first connection that creates the database. See the Properties chapter.



hsql properties
view the connectionnURL
con hsqldb
con derby


31 Jan


31 Jan


31 Jan