All restore operations start with the restore of a FULL backup. It isn’t possible to restore only a Differential or a Log backup.
Both need a reference of the LSN(Log Sequence Number) to proceed.
When we try to restore Differential or Log backup directly without any Full backup, The following Err occurred... Because the differential or log backup will not have LSN to continue.
"The log or differential backup cannot be restored because no files are ready to rollforward."
To identify/verify whether the backup file (LSN) sequence is valid or not
SELECT Name,first_lsn,last_lsn,checkpoint_lsn,database_backup_lsn FROM msdb..backupset WHERE database_name = 'PandianDB' ORDER BY backup_start_date, media_set_id
1. Differential backup Database_Backup_LSN should match with Full Backup Checkpoint_LSN
2. Log backup Database_Backup_LSN should match with Differential Backup Checkpoint_LSN
3. Some times Differential backup and Log backup Checkpoint_LSN are the same. The meaning is "There is no any write operation performed after the Differential backup taken"