The replication job starts when the force interval for small replication jobs is reached. NetBackup SLP settings control how Storage Lifecycle Policy jobs are maintained and executed for the selected primary server. Cohesity documentation identifies these as SLP settings used to customize how SLP jobs run. For AIR replication batching, the controlling parameter here is SLP.MIN_SIZE_PER_REPLICATION_JOB. Official NetBackup documentation defines it as the smallest batch size that can run as a single replication job and states that the job does not run until enough images accumulate to reach that size, or until the force interval for small replication jobs is reached. (veritas.com) In this scenario, three backups of 5GB each create only 15GB of eligible replication data. That is below the configured 20GB threshold, so NetBackup does not start the replication job based on size. Because the backup window has closed and no additional backup images will arrive, the batch cannot reach 20GB. NetBackup therefore submits the small replication batch when the oldest image reaches the configured 60-minute force interval. The force interval is specifically designed to prevent NetBackup from waiting too long before submitting a small replication job. (veritas.com)