SQL error 825 indicates that the read operation had to be reissued at least one time, and indicates a major problem with the disk hardware.

Structured Query Language (SQL) is the standard and most widely used programming language for relational databases. It is used to manage and organize data in all sorts of systems in which various data relationships exist. 

Error 825 is also referred to as the read-retry warning, however the condition is for both read and write operations. 

This error lets you know that a retry of the operation was needed and how many times SQL Server had to retry the attempt before it was successful.

Here at Ibmi Media, as part of our Server Management Services, we regularly help our Customers to resolve SQL related errors.

In this context, we shall look into methods to fix this SQL error.

Nature of SQL error 825 ?

As earlier stated, The error 825 is also called as the read-retry warning.

This error tells a retry operation was needed. Also, it tells how many times SQL Server had to retry the attempt before it was successful.

This message doesn't mention that there is a SQL server problem. Instead, it indicates a larger problem with the disk subsystem which may lead to data loss or database corruption if it is not resolved.

Here is a complete error message:

~~
Msg 825, Level 10, State 2, Line 1.
A read of the file ‘D:\SQLskills\TestReadRetry.mdf’ at offset 0×0000017653C000 succeeded after failing 2 time(s) with error: incorrect checksum (expected: 0×4a224f20; actual: 0×2216ee12). Additional messages in the SQL Server error log and system event log may provide more detail. This error condition threatens database integrity and must be corrected. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.
~~

Method to fix SQL error 825 ?

In order to resolve this error, you can try the tips provided below.

1. Check the error log to find clues that explain the problem.

2. This error mainly relates to disk, the disk controllers, array cards, or disk drivers. So make sure to check the disk system.

3. Contact the disk manufacturer for the latest utilities for checking the status of your disk system. Also, check for the latest driver updates.

4. Try moving all files into a new physical drive(on a new hardware LUN). 

Below are the steps to move all files to a new physical drive.

i. First, add a new Drive (for example, X)

ii. Secondly, create the same folder structure as on the D drive.

iii. Then stop the SQL Service.

iv. Now move files from D drive to X drive.

v. Swap the Drive letters (D > Y, X > D, Y > X)

vi. Finally, start the SQL Service. (you might get some permission errors so make sure to set permissions accordingly).

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