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Exchange full/incremental backup

I have read some articles about Exchange full/incremental backups but the way I understand the backup especially of transaction logs is different.

To my understanding, either Full or incremental backup, delete only the Transaction logs that are committed to the Database, the ones that are not committed they will still be in the queue waiting for their turn to be committed.

But in some articles they don't specify that, they only say Full and incremental delete the transaction logs.

Am I correct or wrong ?

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8/22/2022 - Mon
Shreedhar Ette

There are four kinds of online backups of an Exchange database: normal, copy, incremental, and differential. You may be familiar with these terms; however, the meaning that Exchange assigns to each of them differs from conventional usage:

Normal: The backup program backs up the database files (.edb and .stm), patch data, and at least one log file. After backup is complete, the backup program deletes all log files prior to the checkpoint at the time that backup began; this prevents log files from accumulating until they use up all available drive space. Note that in current versions, Exchange no longer keeps patch information in a separate file, but appends a patch header page to the end of the database file when the backup process is complete.

Copy: The same as a normal backup, except that the backup program does not delete old log files, and does not update the database header to indicate that a backup has taken place.

Incremental: The backup program only backs up log files, not database files. Log files since the last normal backup are copied to the backup medium and are then purged from disk. To restore an incremental backup, you must also restore an earlier normal or copy backup because the incremental backup does not contain the database files. Transaction logs from the incremental backup can be replayed after the logs from the full backup are replayed, assuming that there is an unbroken sequence of logs between the two backups.

Differential: The same as an incremental backup, except that the backup program does not delete old log files from disk.

Extracted from the article:

there is a shade over the incremental backup.

the incremental backup  backs up only TL, both the TL  that are already committed to the database and the ones that are waiting to be committed, it makes sense that the incremental backup deletes the TL that were already committed. but the ones that are not committed and waiting to be committed to the DB should still be in the directory and won't be deleted.

is not that correct?
Shreedhar Ette

Incremental Backup purges the commited tranasaction logs.
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<<<Incremental Backup purges the commited tranasaction logs. >>>
leaves the non-committed in the directory.

correct ?
Shreedhar Ette

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