Writing SQL queries to access an IMS database with the IMS Universal JDBC driver
Use the IMS™ Universal JDBC driver to connect to an IMS database for writing SQL queries.
The IMS catalog provides metadata to your application program. You can write SQL queries to access IMS data based on the metadata information available in the catalog database.
If your IMS system does not use the IMS catalog, you can use the IMS Enterprise Suite Explorer for Development instead.
The IMS Explorer for Development generates a Java™ database metadata class. This class that contains the PSB and DBD metadata classes that the IMS Universal drivers use at runtime.
The metadata includes information about the IMS database, including segments, segment names, the segment hierarchy, fields, field types, field names, fields offsets, and field lengths.
The metadata is used by the IMS Universal JDBC driver to allocate program specification blocks (PSBs), issue DL/I calls, perform data transformation, and translate SQL queries to DL/I calls.
The following table summarizes the mapping between IMS database elements and relational database elements.
| Hierarchical database elements in IMS | Equivalent relational database elements |
|---|---|
| Segment name | Table name |
| Segment instance | Table row |
| Segment field name | Column name |
| Segment unique key | Table primary key |
| Foreign key field | Table foreign key |
- SQL keywords supported by the IMS JDBC drivers
The SQL support provided by the IMS classic JDBC driver and the IMS Universal JDBC driver is based on the SQL-92 standard for relational database management systems. - SQL aggregate functions supported by the IMS JDBC drivers
The IMS classic JDBC driver and the IMS Universal JDBC driver support SQL aggregate functions and related keywords. - Portable SQL keywords restricted by the IMS Universal JDBC drivers
If you use any of
the following SQL keywords as a name for a PCB, segment, or field,
your JDBC application will receive an error when it attempts an SQL
query. Instead, use the aliasing feature of the IMS Enterprise
Suite Explorer for Development.
These keywords are not case-sensitive.
- SQL statement usage with the IMS Universal JDBC driver
The following usage rules apply to SQL statements passed to IMS with the IMS Universal JDBC driver.
