FastCompression Options explanation - what's the difference between "Check Full backup file exists prior to performing a differential backup" on the General tab and the on the Options tab of the Fast Compression Maintenance Plan Fast Compression task
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On the General tab of the Fast Compression Maintenance Plan Fast Compression task:
The Self-Contained Backup Sets option automatically verifies the Full backup exists.
The Separate Backup Files option performs the same validation by default, but Fast Compression includes an option to not perform this check.
On the Options tab of the Fast Compression Maintenance Plan Fast Compression task:
Backup Escalation
This option causes LiteSpeed to issue a full backup, if one of the following problems is discovered in the current backup set:
1. The full backup is missing.
2. A differential backup is missing from the backup set (excludes backups automatically removed after the specified retention period).
3. LSN verification fails in the backup set.
4. Verify operation fails on full or differential backup.
Note: If a problem is detected and a full backup is created through escalation, an informational error message will be returned.
Full backup escalation is selected by default to maintain high recoverability level in the situations where recoverability may be limited
(missing differential in set) or not available at all (missing full backup). This setting provides insurance against unanticipated errors.
For example, if a backup file is missing from the backup set (someone accidentally deleted it), or there is some other type of issue like a Log Sequence Number (LSN) validation error or file corruption, you would not normally be able to restore the database. To correct for this potential issue with backups, Fast Compression automatically runs a full backup to put the database in a restorable state. Errors are still noted in the LiteSpeed Console and alerts will still be sent via the job.
NOTE: If you uncheck this option and Fast Compression discovers an issue (missing file), you will have to correct the problem manually.
If the physical file for the last full backup cannot be found, a differential backup may be executed successfully, but you will not be able to recover the database using these backups unless the correct full backup is located.
Correction may require forcing a full backup using the "@ForceFull = 1" parameter.
Under normal operating conditions, you should not experience these types of issues as they are normally caused by accidental deletion of files or disk corruption, both of which occur very infrequently.
