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Thursday, 23 September 2021

How to Design Backups in SQL Server?

The Recovery Point Objective (RPO) and Recovery Time Objective (RTO) are basic concepts related to the information to be recovered and the time that it will take to recover. In a Recovery Design plan, it is essential to define the time required to restore the data and how much data we can lose in the recovery.

The RPO defines the objective related to the point of recovery. In some cases, we can lose one hour of data, and sometimes we can lose 1 entire day of data. Therefore, defining the RPO at the beginning is critical to design the plan. The same applies to the RTO.

In this article, we will talk about both RPO and RTO, and also discuss how to design the right backup and restore strategy.

Recovery Point Objective (RPO)

Recovery Point Objective (RPO) is a proportion of how often it is necessary to take backups. On the off chance that a disaster happens between backups, would you be able to stand to lose ten minutes of information refreshes? Or then again ten hours? Or then again, an entire full day? RPO addresses how new recuperated information will be. The RPO shows the measure of information (refreshed or made) that will be lost or should be restored after a blackout.

Recovery Time Objective (RTO)

Recovery Time Objective (RTO) isn't just the length of time between the disaster and recovery. The goal additionally represents the means IT team should take to reestablish the application and its information. In the event that IT team has put resources into failover administrations for high-need applications, they can securely communicate RTO in short order.

How to Design the Right Backup and Restore Strategy to Meet Business Goals?

To reduce the RTO, you need to consider combining the transaction log backups and differential backups in your strategy. If you only make full backups, the time to restore the data may be too high. Using differential backups can help reduce the recovery time.

Here are some tips to consider when doing a backup:

  • Make sure to store the backup on a different server. This will prevent you from losing data in case the server is damaged.
  • Use fast hard disks. The backup and restore will be faster if you use hardware with good performance. This will help reach the RTO.
  • Use differential backups to reduce the number of transactional files used to restore. The differential backups allow to restore the data faster and to get the RTO.
  • Estimate how often the data changes. If your data does not change too much during the day, you can make one single differential backup each day and a weekly full backup. On the other hand, if your database has several transactions per minute, you will need to combine full, differential, and transactional backups to recover all the data in the correct RPO.
  • Always test your backup and make sure that RPO and RTO are accomplished on your tests. You will test that the integrity of the data is fine. It is recommended to have a production environment and a testing environment to verify the backups.
  • Make sure to automate the backup and restore strategy by using jobs. The backups should run in a schedule that depends on how the RTO and RPO are designed.
  • If your database is big, using the MAXTRANSFERSIZE and the BUFFERCOUNT may help. These arguments will allow you to increase the size and the buffer. This way you will be able to restore the database faster.
  • Use database and backup compression to increase the speed of the backup.

 Use Stellar Repair for MS SQL for Faster Recovery

There is also another way to recover information in a fast and secure way. Stellar Repair for MS SQL is a well-known third-party software that helps recover data from a corrupt or damaged database. It can also repair damaged databases. If you want to know more about this software, please visit the website here.

Wednesday, 7 July 2021

How to Fix SQL Database Error 8961?

Running DBCC CHECKDB or DBCC CHECKTABLE on a database may report error 8961. Such a situation could occur while changing the data type of a table column from “ntext to nvarchar(max)” and updating the table with over 4000 records.

Essentially, updating the database table (in SQL Server 2012, 2014, or 2016) with 4000+ records leads to corruption. As a result, you get the following error message:

Msg 8961, Level 16, State 1, LineNumber

Table error: Object ID, indexID, paritionID, allocUnitD (type LOB data). The off-row data node at page (PageID), slot 0, textID does not match its reference from page (PageID), slot 0.

The complete error message looks similar to:


What Causes SQL Error 8961?

This is a corruption bug in the SQL Server engine. The corruption occurs within the Large Object (LOB) column.

How to Fix SQL Error 8961?

Microsoft has released the following cumulative updates to fix the database corruption error 8961:

Cumulative Update 5 for SQL Server 2016 RTM

Cumulative Update 2 for SQL Server 2016 SP1

Cumulative Update 4 for SQL Server 2014 SP2

Cumulative Update 11 for SQL Server 2014 SP1

Cumulative Update 7 for SQL Server 2012 Service Pack 3

Apply the cumulative update based on the SQL Server version you are using.

What If the Error Persists?

If applying the cumulative updates doesn’t help resolve the issue, to work around this issue do the following:

Note: Before trying out the below workarounds, investigate the hardware like drivers for I/O subsystem to check if corruption occurs due to hardware problem. If the hardware is faulty, contact your vendor or hardware manufacturer for further assistance.

  • Set the “large value types out of row” Option to 1

After changing the data type, also change the “large value types out of row” option to 1 by executing the query:

ALTER TABLE tbl_Name ALTER COLUMN COLUMN_NAME nvarchar(max) NOT NULL

go

exec sp_tableoption 'tbl_Name', 'large value types out of row', '1'

  •  Restore Records from Backup

If the above workaround fails to fix the error, try resolving the problem by restoring the database from a good known backup. If you don’t have a valid backup, skip to the next method.

  • Run DBCC CHECKDB with Repair Option

As a last resort, you may try running the DBCC CHECKDB command using the minimum repair level, i.e., “REPAIR_ALLOW_DATA_LOSS”.

DBCC CHECKDB (‘db_name’, REPAIR_ALLOW_DATA_LOSS)

 But, this may delete the rows from the table.

  • Use SQL Database Repair Tool

To repair a severely corrupt SQL database and retrieve all the records, try using a third-party SQL database repair tool. Stellar Repair for MS SQL is one such tool that is built to safely scan and fix a corrupted SQL Server database. It supports repairing a db on SQL Server 2019, 2017, 2016, and earlier versions. The software repairs database files (.mdf and .ndf) and recovers all the objects like table, deleted records, stored procedures, etc.

Conclusion

DBCC CHECKDB may report database corruption error 8961 when the data type of a table column is changed and the table is updated with 4000+ rows. The issue occurs due to a corruption bug within the SQL Server engine. To fix this, try installing the latest cumulative updates released by Microsoft. If this doesn’t work, try the workarounds discussed above to fix the 8961 error. If you are required to repair the database, a better alternative is to use SQL database repair tool. The tool can help fix the error with no added risk of data loss.

Monday, 24 May 2021

How to Repair a Database in SQL Server Management Studio

As a SQL database administrator, it’s your responsibility to maintain and secure the databases. However, you may still experience database corruption. If not handled correctly and on time, you may lose potential data. This post will discuss how you can repair database in SQL Server Management Studio (SSMS) when there is no backup. Also, we will discuss an alternative solution to repair a SQL database without data loss risk. But let’s first discuss the possible reasons that can result in database corruption.

Possible Reasons for SQL Database Corruption

  • Server crashes or the system shuts down abruptly in the middle of processing data
  • I/O subsystem failure
  • Bug in the SQL software

You can call your hardware vendor for support to fix issues with the hardware. If the problem is with your SQL software, check out for updates released by Microsoft to fix the bugs in SQL Server. However, in case of a system crash or abrupt system shutdown, you will need to repair the corrupted database to recover its data. 

Before We Proceed

Make sure that your system meets these prerequisites:

  • SSMS must be installed on your machine. If it is not installed, you can download and install it from here.
  • SQL must be installed on your PC.

Steps to Repair Database in SQL Server Management Studio

  • Launch SQL Server Management Studio and connect to a server instance.
  • In the Object Explorer window, click the ‘+’ sign to expand databases.
  • Right-click on a database that you want to repair, and then select Properties. 
  • In the ‘Database Properties’ dialog box, click the Options tab from the left pane. In the Options screen, scroll down to the bottom of the screen.
  • To repair a SQL database, you will need to set it to single-user mode. For this, Restrict Access to SINGLE_USER from MULTI_USER. Click OK. 
You can also set the database to single-user mode by executing the following query:

ALTER DATABASE Test SET SINGLE_USER


Here ‘Test’ is the name of the database that needs to be repaired, replace it with your corrupted database.

Now, to repair the SQL database, you need to run the DBCC CHECKDB command with any of these repair options: REPAIR_FAST, REPAIR_REBUILD, and REPAIR_ALLOW_DATA_LOSS.

REPAIR OPTIONS

Description

REPAIR_FAST

It only maintains the syntax for backward compatibility and does not perform any repair actions.

REPAIR_REBUILD

It helps perform quick repair tasks without any data loss. It can be used for repairing missing rows in nonclustered indexes and rebuilding an index. It cannot repair errors associated with FILESTREAM data.

REPAIR_ALLOW_DATA_LOSS

It can repair all the errors reported by DBCC CHECKDB. But, Microsoft advises on using this option as a last resort to repair the SQL database, resulting in data loss.


Note: You can try using a SQL Recovery Software, such as Stellar Repair for MS SQL to fix all types of corruption errors. It can help repair a SQL database without any data loss risk. 

Click ‘New Query’ from the main menu. 


In the query window that opens, copy and paste the command below:

DBCC CHECKDB ('DB_Name’, REPAIR_ALLOW_DATA_LOSS | REPAIR_FAST | REPAIR_REBUILD) WITH ALL_ERRORMSGS, NO_INFOMSGS;

GO

In the above command, replace ‘DB_Name’ with the name of your corrupted SQL database. And choose one of the repair options. Here’s an example of using the DBCC CHECKDB with ‘REPAIR_ALLOW_DATA_LOSS’ option to repair the database.


  • Click the Execute button to run the query.
  • This will repair the database. Change the database mode from ‘SINGLE_USER’ to ‘MULTI-USER’ by performing steps 4–6 above. Make sure to close and re-launch the SQL Server Management Studio for the changes to take effect.

How Can I Recover Missing Data after Running DBCC CHECKDB?

If you find missing data in the repaired database after running the DBCC CHECKDB with REPAIR_ALLOW_DATA_LOSS command, consider using a SQL repair tool. Recommended by DBAs and MVPs worldwide, Stellar Repair for MS SQL is a reliable software you can use to handle corruption errors in a SQL database. It helps repair a severely corrupted MDF/NDF file on Windows as well as Linux systems.

The software recovers all the database objects, like tables, views, keys, stored procedures, etc., without making any changes to the original database structure. It also helps recover deleted records.

Conclusion

This article outlined the most common reasons leading to SQL database corruption. While restoring from backup is the most recommended and obvious choice to deal with database corruption, there are times when the backup is not updated or has turned corrupt. In that case, you need to try repairing the database. This article covered the step-wise instructions following which you can repair the database in SQL Server Management Studio. Also, it advised using a SQL recovery tool as an alternative to DBCC CHECKDB with the REPAIR_ALLOW_DATA_LOSS command. 

Monday, 8 March 2021

Stellar Toolkit for MS SQL - Software Review

As a SQL database administrator, I am responsible for maintaining our organization's SQL Server and databases. But despite implementing best database maintenance practices, including backups and performing DBCC CHECKDB integrity checks, I still run into database issues. Among these, corruption of SQL Server database is one of the most common issues that I've encountered as a DBA.

My recent experience with database corruption, which nearly made me lose my data due to corrupted database backup, made me think about an alternative approach. This was when I came across Stellar Toolkit for MS SQL, a software package comprising tools to repair corrupt SQL database, extract data from a corrupted backup file, and reset password of the database files.

Today, I'll be sharing my experience with Stellar Toolkit for MS SQL. For this review, follow the step-wise instructions below once you have downloaded and installed the software:

Stellar Repair for MS SQL

  • Launch Stellar Toolkit for MS SQL. This will open the following window:


  • Select 'Repair MS SQL Database.' The SQL repair software main interface opens with an instruction. The instruction suggests stopping the SQL server and creating a copy of the database (.mdf) file to be repaired. After creating the MDF file copy, you can restart the server and repair the db copy. 

  • Clicking OK opens a 'Select Database' window. Click on 'Browse' to select the corrupt MDF database file that you want to repair. If you're not aware of the file's location, click 'Search' to locate and select the file. After selecting the corrupt database file, click 'Repair' to begin repairing it.

  • Once the repair process is complete, a 'Repair complete' message box appears along with a preview of all recoverable database objects and the repair process's log report.


  • After verifying the recoverable data, clicking 'Save' on the File menu opens a Save Database dialog box with options to save the repaired file. The file can be saved in multiple file formats, such as MDF, CSV, HTML, or XLS. To proceed with saving the file, you'll need to connect to an instance of SQL Server to create a new database or overwrite an existing db. Finally, click the 'Save’ button for saving the repaired SQL Server database file to the selected location. 

Stellar Password Recovery for MS SQL

The toolkit's second tool is useful for admins who have lost or forgotten the password of their SQL database files. It helps in resetting the password of a protected database in just a few clicks; here’s how:

  • Select ‘Recover MS SQL Password’ from the main interface. This will open the Stellar Password Recovery for MS SQL interface as shown below:


  • Next, all you need to do is click ‘Browse’ to select your SQL database file (MDF), and then click the ‘Change Password’ button. This will reset the password of the selected database file. 

Note: You may not be able to problem selecting the backup (.bak) file if any MDF file is in use. So, make sure to stop the SQL Server service before resetting the password.

After resetting the password, exit the Password Recovery tool, restart the SQL Server service, and then try connecting to your server instance using the reset password. 

Stellar Backup Extractor for MS SQL

Another tool available in the toolkit is the backup file extractor. It helps recover data from a corrupted SQL database backup (.bak) file. Also, the tool provides different scan modes to perform quick or deep recovery of backup data.

The steps to recover data from corrupted backup file are as follows:

Click ‘Extract from MS SQL Backup’ to open the Stellar Backup Extractor window. The window opens with options to browse or search the corrupt backup (.bak) file. Once the file is selected, click Scan to initiate the scanning process.

  • The tool then asks to select an appropriate scan mode to perform the recovery. It recommends running the ‘Standard Scan’ to analyze a corrupted SQL backup file quickly. If you’re not satisfied with the Standard Scan results, choose ‘Advanced Scan’ for a severely corrupted backup file. After selecting the desired scan mode, click ‘OK’.

  • A window opens asking to select the type of backup you want to recover. 

  • Once you’ve selected the backup type, click Next. A ‘Repair Complete’ dialog box opens on successful completion of the SQL backup process. Click ‘OK’ to preview the recoverable data along with log report of the entire backup recovery process.  

  • After verifying the recoverable backup file data, click ‘Save’ on the ‘File’ menu to save the recovered file.

Conclusion

Stellar Toolkit for MS SQL is an effective utility that you can rely on to resolve major database issues. Having this tool at your disposal can help you reduce downtime associated with troubleshooting SQL database issues, as it provides tools to perform database repair, backup recovery, and reset passwords in a single interface.