Context
A SQL Server transaction-log chain is a continuous history used to roll a restored database forward. Backups that look sequential in a directory can still belong to different databases, differential bases, or recovery branches. Build the restore sequence from metadata and the intended recovery point before starting the recovery operation.
Prerequisites
Identify SQL Server version, recovery model, database identity, target recovery point, available full and differential backups, and log artifacts from every producer. Confirm encryption material and storage access. Use a separate recovery instance with sufficient capacity. This guide concerns databases using the full or applicable bulk-logged recovery workflow; review the installed release's restrictions for the exact target and operation.
Construct the sequence
- Inventory backup sets with their authoritative metadata, not only filenames and timestamps. Use supported read-only inspection such as
RESTORE HEADERONLYthrough the approved tooling. Record database identity, backup type, LSN-related fields, recovery branch information, and file or media identity. Retain the original artifacts while building the plan. - Select a usable full backup and, if appropriate, a differential with the correct base. A newer-looking differential is not valid merely because its filename sorts later. Check the required base relationship and target recovery point. Include backups created on other availability-group replicas or by another approved backup producer when applicable.
- Identify all log backups needed to bridge from the selected data backup state to the intended point. Check metadata continuity and recovery-branch compatibility rather than demanding simplistic equality between every displayed LSN field. Overlapping log coverage can occur. Use the engine's documented restore rules and rehearse the actual sequence to establish applicability.
- Restore the reviewed sequence only on the isolated target. Keep the database unrecovered while additional log backups remain to be applied, using the documented
NORECOVERYworkflow. Recover it after the final intended input. Recovering too early prevents applying later logs in that sequence and can require restarting from the data backup.
Diagnostic table
| Finding | Likely planning issue | Next action |
|---|---|---|
| Log file missing from required interval | Coverage gap | Search approved producers and archives |
| Differential rejects selected base | Base mismatch | Inspect backup metadata |
| Log rejected after early recovery | Sequence ended prematurely | Rebuild and repeat isolated sequence |
| Dates look right, branch differs | Different recovery history | Review branch-aware restore plan |
Illustrative scenario
Backups are collected from two availability-group replicas. The recovery folder contains logs from only one producer, leaving an apparent gap after a scheduled job moved. The team queries the central inventory, retrieves the missing applicable artifacts, and completes a test sequence. Sorting one server's directory would not have represented the database's complete backup history.
Correct and verify
If a required log is unavailable, record the latest achievable recovery point and escalate that business decision. Do not alter backup headers or force later logs onto an incompatible state. After isolated recovery, verify database integrity and selected business records around the intended boundary. Preserve engine output and the exact artifact list so another operator can reproduce the result.
Operating procedure
Maintain a central manifest across all backup producers, with artifact identity and metadata sufficient to reconstruct the sequence. Alert on missing log-backup intervals and failed transfers. Periodically restore a retained chain, including older data backups, rather than checking only the latest full backup. Review the chain after recovery-model changes, restore events, and backup-tool migrations.
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