SQL Saturday #662 Sioux Falls

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1 SQL Saturday #662 Sioux Falls

2 Help! Help! My system databases are gone! Marcus Hopfinger

3 Please be sure to visit the sponsors during breaks and enter their end-of-day raffles! Remember to complete session surveys! You will be ed a link after the event or you visit tion.aspx Event After Party At Will s Training Table (Formally Beef O Bradys) near the Pentagon starting at 5:45 PM Want More Networking and Training? (605) SQL meets the 2 nd Tuesday of every month.

4 STI Special thanks to Southeast Technical Institute for this the use of this awesome facility!

5 Thank You Sponsors

6 About me Name: Marcus Hopfinger Job: Database Administrator Company: Daktronics, Inc. ( Duration: Over 16 years working with SQL Server. First experience with SQL Server: SQL Server 7

7 Situation The drive that hosts your system database files (not C:\ right?) is corrupt or has crashed. The drive with the executables is still intact.

8 Prerequisites for recreating/restoring files Before you get started you will need the appropriate ISO for your version and edition of SQL Server. You will need a replacement drive, with the same letter(s) as the old drive(s), created in order to restore your system databases. And, of course, good recent backups of your system databases.

$needed: E:\>Setup /QUIET /ACTION=REBUILDDATABASE /INSTANCENAME=MSSQLSERVER /SQLSYSADMINACCOUNTS="domain\YourLogin"$

9 The recreation process Mount your ISO From Command Prompt run the following changing the drive letter and account information as needed: E:\>Setup /QUIET /ACTION=REBUILDDATABASE /INSTANCENAME=MSSQLSERVER /SQLSYSADMINACCOUNTS="domain\YourLogin"

10 The recreation process Process Complete

$C:\Program Files\Microsoft SQL Server\ \MSSQL\Data$

11 C:\Program Files\Microsoft SQL Server\ \MSSQL\Data You should now have system data and transaction log files

12 The restore process In SQL Server Configuration Manager in the Startup Parameters add the m flag to start SQL Server in single user mode.

13 The restore process Now in SQL Server Management Studio you can connect a query window, not object explorer, and use a query to restore master database. RESTORE DATABASE master FROM DISK = 'C:\IT\master_backup_2017_08_19_140813_ bak' WITH REPLACE You could also do this from SQLCMD if you prefer. Before running this you need to make sure that new drives with the same drive letters have been created for all system databases.

14 The restore process Once the restore completes it will stop SQL Server. Remove the -m flag Update the location for master database under Startup Parameters Copy the newly restored data and log files to the correct locations Start SQL Server and reconnect SQL Server Management Studio Restore msdb; just be sure the SQL Agent service isn t running Restore model and distribution if needed as well

15 What happens if an.ldf file goes missing?

16 Missing transaction log If the database was cleanly detached and the LDF gets deleted it can be recreated by using one of the following scripts: CREATE DATABASE [YourDatabase] ON (FILENAME = 'S:\SQL_DATA\YourDatabase.mdf') FOR ATTACH; CREATE DATABASE [YourDatabase] ON (FILENAME = 'S:\SQL_DATA\YourDatabase.mdf') FOR ATTACH_REBUILD_LOG; EXEC = = 'S:\SQL_DATA\YourDatabase.mdf'; If SQL Server has been cleanly shutdown and an LDF gets deleted my testing shows that when SQL Server is restarted it will recreate the LDF.

17 Missing transaction log If SQL Server crashes and your transaction lost you can recreate the file but you WILL lose transactions that weren t written to the MDF. After the crash you get SQL Server started and you see your database but it shows as Recovery Pending Best case is the location for your LDF is still present or can be recreated. If so you can bring the database back online using the following scripts however any un-checkpointed transactions will be lost. ALTER DATABASE [YourDatabase] SET EMERGENCY; ALTER DATABASE [YourDatabase] SET SINGLE_USER; DBCC CHECKDB([YourDatabase], REPAIR_ALLOW_DATA_LOSS); ALTER DATABASE [YourDatabase] SET MULTI_USER;

18 Missing transaction log You will see the following messages before the DBCC results: File activation failure. The physical file name "L:\SQL_LOGS\Chinook_log.ldf" may be incorrect. The log cannot be rebuilt because there were open transactions/users when the database was shutdown, no checkpoint occurred to the database, or the database was read-only. This error could occur if the transaction log file was manually deleted or lost due to a hardware or environment failure. Warning: The log for database 'Chinook' has been rebuilt. Transactional consistency has been lost. The RESTORE chain was broken, and the server no longer has context on the previous log files, so you will need to know what they were. You should run DBCC CHECKDB to validate physical consistency. The database has been put in dbo-only mode. When you are ready to make the database available for use, you will need to reset database options and delete any extra log files. DBCC results for 'Chinook'.

19 Missing transaction log If the data files must be moved to a different server after a crash a hack attach must be used. On a server of the same version as the database: Create a new empty dummy database of the same name and structure number of files and the file names must be the same must be the same as the database to be recovered. Take the new database offline and replace the data files with the ones from the crashed server Bring the database online, you will receive an error message just click OK It should now show as recovery pending User the previous scripts to make the database useable

20 What happens if a data file goes missing?

21 Missing data file This is the easiest situation. If your database is in full or bulk-logged recovery model you need to immediately back up the tail of the transaction log. BACKUP LOG [YourDatabase] TO DISK = V:\SQL_BACKUPS\YourDatabase_tail.trn' WITH INIT, NO_TRUNCATE;

22 Missing data file Now restore your full backup and roll forward all the transaction log backups (make sure you use WITH NORECOVERY!) up to and including the tail of the log backup. Once you have triple checked everything is good to go run RESTORE DATABASE [YourDatabase] WITH RECOVERY;

23 More information Regenerating system databases: Regenerating LDF files: Hack Attach: Emergency Mode Repair:

24 Questions?

25 Contacting me: LinkedIn: Blog:

SQL Saturday #654 - Omaha

SQL Saturday #654 - Omaha My Top 10+ Favorite Replication Tricks Marcus Hopfinger About me Name: Marcus Hopfinger Job: Database Administrator Company: Daktronics, Inc. (www.daktronics.com) Duration: Over