A read operation on a large object failed while sending data to the client. A common cause for this is if the application is running in READ UNCOMMITTED isolation level. This connection will be terminated.

SELECT is_read_committed_snapshot_on FROM
sys.databases WHERE name= 'confluence_database';

If this query returns a value of 1, it means the correct isolation level is set. If it's not set, please refer to our Database setup for Microsoft SQL Server documentation (https://confluence.atlassian.com/display/DOC/Database+Setup+for+SQL+Server#DatabaseSetupforSQLServer-Step3.SetupyourSQLServerdatabaseanduser) - particularly "Setting up the Database".
You should also check the database for consistency by running the following query:

DBCC checkdb

If this query indicates that the database requires repair, proceed to the resolution.

[Note: We've seen this problem occur in Microsoft SQL Server 2014, which is unsupported at time of writing. Please ensure that you're running on a database listed on our Supported Platforms page.

Cause
The database may be corrupted (hence the read errors) and may require repair.
Resolution

• Shut down Confluence
• Complete a full database backup
• Run each query individually, replacing confluence-database with your database name:

ALTER DATABASE "confluence-database" SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
DBCC CHECKDB('confluence-database', 'repair_allow_data_loss');
ALTER DATABASE "confluence-database" SET MULTI_USER;

Restart Confluence

Reference: https://confluence.atlassian.com/display/CONFKB/Repairing+a+Damaged+Microsoft+SQL+Server+Database