iX V6.5 (30391-90011)

378 Chapter8

Using the Database Utilities

Restructuring the Database with TurboIMAGE/XL Utilities

Using the utilities DBUNLOAD, DBUTIL, DBSCHEMA, and DBLOAD, certain changes to the

structure of an existing database, such as capacity changes, adding additional items and

sets, and repacking data sets, can be made without having to write special programs to

transfer data from the old database to the new one. The general sequence of operations to

do this is as follows:

1. Run DBUNLOAD on the old database, copying all the data entries to tape.

2. Purge the old database using the DBUTIL >>PURGE command.

3. Redeﬁne the database using the same database name by modifying the schema ﬁle, and

create a new root ﬁle with the Schema Processor, DBSCHEMA.

4. Use the DBUTIL >>CREATE command to create and initialize the data sets of the new

database.

5. Run DBLOAD on the new database using the tape created in step 1 to put the data into

the new database.

The above procedure allows only the supported structural changes to the schema listed

below. DBLOAD does not prohibit other changes; however, the data is not guaranteed to be

consistent. Supported schema changes yield structurally intact databases and always

result in a good transformation. Commercial software packages are available that can

perform other structural changes without doing a DBUNLOAD and DBLOAD operation.

Supported Structural Changes Using DBUNLOAD and DBLOAD

Any of the following schema changes, alone or combined, always result in a successfully

transformed database:

• Adding, changing, or deleting passwords and user class numbers.

• Changing a data item or data set name and all references to it.

• Changing data item or data set read and write class lists.

• Adding new data item deﬁnitions.

• Removing or changing deﬁnitions of unreferenced data items.

• Increasing data set capacities.

• Adding, deleting, or changing sort item designators.

• Adding and deleting automatic master paths.

Unsupported Structural Changes Using DBUNLOAD and LOAD

The following structural changes are legitimate only in certain circumstances and can

result in data set discrepancies or lost data:

• Changing primary paths.

• Adding new data items to the original end of a data entry deﬁnition.