SQL DBA Blog: Home
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The Query Is Fast in SSMS but Slow From the Application
The same query returns instantly in SSMS and crawls from the application. SSMS connects with ARITHABORT ON and a .NET client connects with it OFF, so the plan cache holds two plans for one query. The query that proves it, and the fixes in order.
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The Log in This Backup Set Is Too Recent or Too Early to Apply (Errors 4305, 4326 and 3159)
Restore chain errors 4305, 4326 and 3159: what the two LSNs in the message mean, which file to apply next, and how to back up the tail of the log before you overwrite anything.
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Login Failed: Server Is in Script Upgrade Mode (Error 18401), and How Long to Wait Before You Worry
This is the error every patch window can raise and almost nobody plans for. The Cumulative Update installed, the service came back, and now every application login is refused with 18401. Nothing is broken yet. SQL Server is running the second half of the patch, and it will not let anyone in until that half…
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DBA Scripts: Enable or Disable All SQL Agent Jobs
Turning every SQL Agent job off is easy. Turning the right ones back on is where it goes wrong. Save the state first, disable with sp_update_job, restore from what you saved, and know why disabling does not stop a running job.
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Create a Linked Server to Another SQL Server
Two stored procedures create a linked server, and on a modern instance the first attempt usually fails with a certificate error because MSOLEDBSQL 19 encrypts by default. The fix, plus rpc out, OPENQUERY, Msg 7411 and Msg 7202.
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RESTORE Fails: Exclusive Access Could Not Be Obtained (Error 3101)
Msg 3101 means SQL Server cannot get exclusive access to the database you are restoring. Find the connected sessions, stop clients reconnecting, and retry only when it is safe to disconnect users.
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DROP TABLE IF EXISTS in SQL Server
DROP TABLE IF EXISTS arrived in SQL Server 2016 and replaced a three-line OBJECT_ID check that everybody had memorised. It is a small feature and it is genuinely useful, but there is more behaviour hiding in it than the syntax suggests.
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Add a Filegroup to a SQL Server Database
ADD FILEGROUP then ADD FILE, and the trap in between: a filegroup with no files will accept a CREATE TABLE and only fail at the first INSERT with Msg 622. Placing objects, changing the default, and removing one again.
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Error Locating Server/Instance Specified (Error 26)
Error 26 means the client could not look up a named instance’s port. Check the instance name, the SQL Server Browser and UDP 1434, or connect with server,port.
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How to Search for a String in All Tables in SQL Server
Somebody hands you a database you have never seen and a value: an email address, a reference code, a customer name. Where is it stored? There is no Ctrl+F for a schema, so the job is to build one.
- Cannot Connect to WMI Provider: SQL Server Configuration Manager Will Not Open
- SQL Server Configuration Manager: Where to Find It and What a DBA Uses It For
- DBA Scripts: Get Failed Login Summary
- Query Was Fast Yesterday, Slow Today: Find What Changed
- The Current Transaction Cannot Be Committed (Error 3930)
- Sort and Hash Spills to TempDB: Find the Query and Fix the Grant
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