HP 3000 Manuals HP 3000 Manuals
Before Restructuring the Database
Before you use the DBAPLUS program to restructure the database, be sure
to follow the steps below:
1. Obtain a current backup copy of the database as a precautionary
measure. If the DBAPLUS program is unable to complete the
restructure because of a fatal error, your original database may
be left in an inconsistent state. In this case, you will need to
restore a backup copy of the database.
To be sure you have a current copy, the DBAPLUS program checks if
the database has been modified since the last DBStore. If it has,
the DBAPLUS program asks if you want to continue with the
restructure. You should continue only if you have a backup copy
of the database.
2. Make sure that all security criteria have been met. To use the
DBAPLUS program, you must be logged on as the database creator.
The DBAPLUS program checks that the logged-on user matches the
logon stored in the change file. If it does not, a security
violation message is displayed and the DBAPLUS program terminates.
3. Ensure that adequate disk space is available for the DBAPLUS
program to perform the restructure. To estimate how much disk
space you need, first identify the data sets being altered.
Assume that the DBAPLUS program will use at least as much space as
the data sets currently occupy. Adjust your estimate depending
on the nature of the changes stored in the change file.
Modifications, such as adding new fields or changing data set
capacity, can affect the disk space needed by the new data sets.
The method the DBAPLUS program uses to restructure the database
also affects the disk space needed. Refer to "How DBAPLUS
Restructures a Database" later in this chapter for more
information.
If not enough disk space exists to create all the necessary
temporary files before beginning the restructure, the DBAPLUS
program prompts you to make a choice as listed below. Note,
however, that neither of these methods guarantee that you can
successfully run the DBAPLUS program if you have very large data
sets and very little available disk space.
a. You can choose to exit the DBAPLUS program without
performing the restructure. Before using the DBAPLUS
program again, obtain more disk space or remove some of
your changes from the change file with DBChange and
restructure the database in stages.
b. You can direct the DBAPLUS program to perform the
restructure using an alternate method which uses less disk
space. However, be aware that if a fatal error occurs
during the restructure, the database is left in an
inconsistent state. This method creates one temporary data
set at a time. When the changes are successfully made to
the temporary data set, the DBAPLUS program purges the
original data set. The danger is that if a fatal error
occurs during this process, some of the original data sets
will have been purged before the new ones have been saved.
In this case, you need to run DBUTIL to purge the database
and restore an archival version.