IBM i series Handbook page 490

Operating System/400 (5722-SS1)
users to specify outer joins or exception joins, therefore reducing the number of queries
required. A NULL field is now returned when a file query does not find records that meet the
join criteria. This allows users to develop and use more efficient reports.
Alter Table
The Alter Table function enhances database administration while improving SQL standards
conformance. This function allows the user to add a column, drop a column, or change a
column's attributes for an existing database table. End-user productivity can be greatly
enhanced with this standard conforming function for database changes and administration.
Both SQL and native interfaces are provided.
X/Open Call Level Interface to SQL
Support of the X/Open standard for an SQL Call Level Interface (CLI) allows users to easily
access DB2 UDB for iSeries SQL functions directly from high-level languages (HLL) without
performing an SQL precompile. This standard CLI support also allows SQL access from
languages such as C++ that currently do not have another SQL interface or precompiler.
There is an option to enable writing applications that do database serving for multiple users
(server mode).
The X/Open standard CLI is supported on several other database platforms, which makes
SQL application portability to and from the DB2 UDB for iSeries platform even easier.
SQL Repeatable Read
Support of the standard compliant isolation level, Repeatable Read, enables users to ensure
that, if a specific query is issued in a unit of work multiple times, the same result will be
returned each time by preventing concurrent jobs from changing the queried data. This
isolation level also offers increased interoperability in distributed DB2 and DRDA
environments. Users can also now specify the isolation level (commitment control level) on a
per statement basis for the SELECT, UPDATE, INSERT, and DELETE statements. This
provides greater flexibility when executing under commitment control.
Access to Data Areas and Data Queues
DB2 UDB for iSeries includes support for transparent remote access to data areas and data
queues. Applications that use data areas or data queues for inter-process communications
can be distributed across multiple iSeries servers, providing new options as users move into
distributed iSeries networks and multi-tiered application models. Additional data queue
support is included in MQSeries for iSeries, a separately-licensed program, 5722-MQ1.
Two-phase Commit Transaction Management
Allows applications to access multiple heterogeneous databases simultaneously in complex
client/server and peer-to-peer environments using APPC sync point protocols.
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iSeries Handbook