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Incremental backups: Can they include full backups?

DRAFT COPY - Currently under review and edit.

INTRODUCTION:
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This Progress Technical Support knowledgebase entry deals with the
incremental backup as it relates to the overlap factor (-io).

WHY YOU NEED TO KNOW THIS:
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An incremental backup saves the data that has changed since the
last full or incremental backup was performed. This is useful because
it often takes less time and media to back up the database this way.

In a PROGRESS database, the master block and every database block
contains a backup counter. The counter in the master block is
incremented each time the database is backed up with an on-line, an
off-line, full, or incremental backup.

When you use incremental backups they must be applied in chronological
order to a restored copy of a full backup of the db. Once the database
has been fully backed up again, the counter in the masterblock is
reset and the incremental backups are counted from that point.

However, if you use the -io option, this allows you to decrease the
number of incremental backups which must be applied to your restored
database. For example, if -io = 5, then you only need to apply every
5th incremental backup to your restored database, as these include all
the changes that were made to the database in the preceeding four
increments. -io is cumulative.

IMPORTANT NOTE: Using overlapping factor allows you to treat full
backups of your database as if they were incremented ones. This
is useful if your full backup becomes unavailable, as in the case
when the media for a full backup becomes damaged or inaccessable.
Using the overlapping factor, however, can mean that the incrementals
will include ALL of the full backup preceeding it; after all, creating
a full backup means that the entire database has "changed" (because
each block has been read and written in the process). Consequently,
it is possible to restore an earlier database and apply incrementals
even if a full backup occurs in the interim.

PROCEDURAL APPROACH:
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To use incremental backups with the overlapping factor, use the
following syntax:

For UNIX and Windows platforms - "probkup db-name devicename -io i"
For VMS - "PROGRESS/BACKUP/BLOCKING_FACTOR=N dbname devicename

For restores, you use the following syntax:

For UNIX and Windows platforms - "prorest dbname incrementalname"
For VMS - "PROGRESS/RESTORE dbname MAD$DAT

NOTE: if you are storing an incremental backup, using overlapping
factor, AND you are including a full backup of the database as one
of your incrementals, you will see the following message:

This is an incremental backup of <fulldbname>. This backup was taken
at <time/datestamp>. It is based on the full backup of <last full
backup>. It will require x blocks to restore.
WARNING: This incremental was done for full backup dated <last full
backup> and last full restored to this database is dated <earlier
full backup>.
Do you want to continue?

THE ANSWER TO THIS QUESTION IS "YES".

REFERENCE TO ON-LINE OR DOCUMENTATION:
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A full summary of backup and restore procedures is found in your
System Administration Guide, Chapter 11.

See also AFTER IMAGE

Progress Software Technical Support Note # 17876