2.1.2 Concept Overview
3. An initial full backup must be taken with the BACKUP subcommand. This full backup establishes the parent of the first incremental backup.
5. Incremental backups are taken using the BACKUP subcommand with the --parent option to specify the backup identifier or name of a previous, full backup or an incremental backup. Any previous backup may be chosen as the parent as long as all backups belong to the same timeline.
6. The incremental backup process identifies which WAL files may contain changes from when the parent backup was taken to the starting point of the incremental backup. The corresponding MBM files are used to locate and copy the modified blocks to the incremental backup directory along with other database cluster directories and files. Instead of backing up all, full relation files, only the modified blocks are copied and saved. In addition, the relevant MBM files are condensed into one consolidated block map (CBM) file that is stored with the incremental backup. Note: Multiple block copier threads can be used to copy the modified blocks to the incremental backup directory. See sections 4.1 and 4.2.5 for setting the thread_count parameter in the BART configuration file. See Section 5.4.3 for using the --thread-count option with the BACKUP subcommand.
7. The restore process for an incremental backup is invoked using the RESTORE subcommand in the same manner as restoring a full backup. The -i option specifies the backup identifier or name of the incremental backup to restore. The restore process begins by going back through the chain of past, parent incremental backups until the initial full backup starting the chain is identified. This full backup provides the initial set of directories and files to be restored to the location specified with the -p option.