Plan for retained log.
Not just the backup interval.

Backup is not shrink.
Truncation is not deletion.

Log truncation makes inactive space reusable inside the existing log file. It does not return that space to the filesystem.

Scenario calculation

Additional generated log = MiB/min × blocked minutes ÷ 1,024. Scenario active demand = starting active log + additional generated log. The larger of scenario demand and observed peak is multiplied by your headroom factor, then rounded upward to 64 MB. The review script retains a larger existing allocation rather than requesting a shrink.

Starting active log is the retained baseline at the beginning of the scenario. The rate should include all concurrent logging during the window. Do not add the observed peak a second time: it is compared with the scenario, not summed into it.

Growth and available time

Growth events are rounded up from the difference between current allocation and modeled capacity, divided by the entered fixed increment. The no-reuse buffer time divides existing free log by the scenario generation rate; it excludes future growth, VLF boundaries and unmodeled workload variation. It is not a live time-to-failure prediction.

Investigate the reason for retention

Long transactions, availability-replica lag, replication/CDC and other reuse waits can retain log. FULL and BULK_LOGGED need an appropriate log-backup strategy, but backups do not remove every blocker. SIMPLE can also retain log because of active transactions and other waits.

Preallocate from measured workload demand. Fixed growth helps control increments; the editable default is an assumption, not a universal optimum. Assess growth latency and VLF layout separately. This tool does not change recovery model, shrink files, remove logs or prescribe backup frequency.