Additional HADB Information

This section describes important additional information about the HADB implementation that is included in Application Server 8.2.

• HADB Enhancements

• Known SQL Limitations

• High-Availability Load Balancing

HADB Enhancements

• A new management command, hadbm setadminpassword, has been implemented to allow changing the password used for database administration. The command takes options indicating which management agent to use, and the old password and the new password. For more information, see the hadbm setadminpassword man page.

• The existing management command, hadbm listpackages, has been modified. Previously, the command took no operands, and listed all packages in the relevant management domain. The modifications introduce an optional package name operand, and list only packages with that name. If the operand is not provided, all packages are listed. For more information, see the hadbm listpackages manpage.

• The existing management command, hadbm createdomain, has been modified. The hostlist operand is extended to also specify the port number of the management agent. In this way, the domain is completely specified by using only the hostlist operand. The old behavior is still supported for backward compatibility. For more information, see the hadbm createdomain manpage.

• Some of the error messages from the management system have been modified. The modifications are intended to improve comprehension, consistency, and accuracy of the error messages. The actual modifications are not listed in these release notes.

• The installation and uninstallation behavior has been slightly changed. Installing or uninstalling the HADB should always preserve the link /opt/SUNWhadb/4, but this has not always been the case.

• The possibility of typing passwords on the command line as a command option is deprecated. This deprecation is relevant to all hadbm commands that accept passwords as command-line options. For hadbm commands, it has previously been possible to type a password as:

  1. A password file

  2. A command line option

  3. An interactive input

  The command-line option is considered unsafe and is therefore deprecated. A warning message is issued if a password is typed in this way. Instead, use a password file or interactive output. Note this applies to all hadbm commands that accept a command-line password option.

• HADB has been upgraded to use JGroups Version 2.2, and its source code is distributed along with the HADB. To support online upgrade from a previous HADB version, both JGroups 2.1 and 2.2 are delivered with HADB. For JGroups 2.1, byte code is delivered only.

Known SQL Limitations

• You cannot create a UNIQUE secondary index on a table.

• The expression (DISTINCT column) is not allowed in an aggregate expression, unless this is the only selected expression.

• All tables must be created with a primary key specification. That is, tables without primary keys are not supported.

• FULL OUTER JOIN is not supported.

• IN subqueries that are table subqueries are not supported, for example:

  SELECT SNAME FROM S WHERE (S1#,S2#) IN (SELECT S1#,S2# FROM SP WHERE P#='P2')

• Constraints other than NOT NULL and PRIMARY KEY are not supported.

• You can assign a new owner to a resource. When making this change, however, privileges granted to the current owner are not granted to the new owner.

• Queries with two or more nested NOT EXISTS subqueries where each subquery is not directly correlated to outer level of queries is not supported.

• Column privileges are not supported.

• Row value constructors are allowed only in a VALUES clause.

• Subqueries are not accepted as value expressions in row value constructors.

• The following data types cannot be used when creating primary keys:

  • REAL

  • FLOAT

  • DOUBLE PRECISION

  • DECIMAL

  • NUMERIC

High-Availability Load Balancing

The Application Server includes load balancing for the following:

• HTTP, IIOP, and JMS clients

• HTTP session failover support

• EJB clustering and failover support

• Highly available EJB timers

• Distributed transaction recovery

• Support for rolling application upgrades

• High-availability database for storing the transient state of J2EE applications

Availability allows for failover protection of Application Server instances in a cluster. If one Application Server instance fails, another Application Server instance takes over the sessions that were assigned to the unavailable server. Session information is stored in the HADB. HADB supports the persistence of HTTP sessions, Stateful Session Beans, and Single Sign On credentials.