TurboIMAGE/XL Database Management System Reference Manual (30391-90012)

Chapter 8 381
Using the Database Utilities
Restructuring the Database with TurboIMAGE/XL Utilities
• Removing data items from the original end of a data entry definition.
• Changing an automatic master to a manual master or vice versa.
• Adding or deleting a data set at the end of a schema.
• Changing the native language definition for the database.
These are unsupported schema changes. DBLOAD does not prohibit these changes; however,
the data is not guaranteed to be consistent. A change must be judged in light of the
particular database and the functioning of DBUNLOAD and DBLOAD, described later in this
chapter.
Basically, all entries from an old data set are put into the corresponding new data set,
except that no entries are directly put into automatic masters. The entries are truncated or
padded with binary zeros as necessary to fit the entry length of the new data set. DBUNLOAD
and DBLOAD always handle full entries, without regard to item positions or lengths. If the
new data set entry is defined with the items in a different order than the old data set,
DBLOAD may not fail but the data set entries, nevertheless, will be invalid. For example,
data of type real may now occupy the position of a character type item.
The number of the data set is determined by the order in which the data sets we re entered
in the schema file. Therefore, because data sets are loaded by number, additions and
deletions should be made at the end of the schema. Data set one would correspond with the
first data set appearing in the schema. DBLOAD always returns a warning if it detects a
discrepancy between the number of data sets defined in the schema and the number of
data sets on the DBLOAD media, but you can allow DBLOAD to continue after the warning if
you are confident that the database will not be corrupted.
In some circumstances, the load completes, but data is lost. For example, data is lost if the
capacity of a data set is reduced in the new database to less than the number of data set
entries on the tape. If this is not desired, increase the capacity of the data base and restart
the DBLOAD process (refer to "Restructuring the Database with TurboIMAGE/XL Utilities"
earlier in this chapter.)