To Modify .ndf (secondary data) Files from the Tempdb database in SQL Server.

SQL Tempdev creates multiple .ndf  files and keeps increasing that cause the drive C: became full.

Resolution: Modify the the NDF files and assign fix file sizes.

Important Considerations

• You cannot remove a tempdb file while SQL Server is running.

• File changes to tempdb must be made via ALTER DATABASE, and SQL Server must be restarted for the changes to take effect.

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✅ Step-by-step Process to Modify .ndf Files from tempdb

1. Identify the .ndf Files

Run this query to list all tempdb files:

SQL:
USE tempdb;
GO
EXEC sp_helpfile;

This will list .mdf, .ldf, and any additional .ndf files.

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2. Alter the tempdb to Modify the .ndf Files

You can modify each file using this command:

sql:

USE master;
GO
ALTER DATABASE tempdb MODIFY FILE tempdev2;
-- Replace tempdev2 with the logical name of the .ndf file

Repeat for each .ndf file.

Note: If the file is in use, this command will fail. Since tempdb is re-created every time SQL Server restarts, this command prepares the configuration for the next restart.

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3. Restart SQL Server

After successfully executing the ALTER DATABASE command(s), restart the SQL Server instance for the changes to take effect.

• You can do this through SQL Server Configuration Manager or Services.msc.

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4. Verify Removal

After restart, check again:

sql:

USE tempdb;
GO
EXEC sp_helpfile;

The .ndf files should change the file size.

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To reconfigure tempdb for a 10-core SQL Server using 6 evenly sized data files (tempdev, tempdb2–tempdb6), all placed in the same default directory.

USE master;

GO

-- Primary data file (tempdev)

ALTER DATABASE tempdb

MODIFY FILE (NAME = tempdev, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

-- Secondary data files (temp2 to temp8)

ALTER DATABASE tempdb

MODIFY FILE (NAME = temp2, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

ALTER DATABASE tempdb

MODIFY FILE (NAME = temp3, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

ALTER DATABASE tempdb

MODIFY FILE (NAME = temp4, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

ALTER DATABASE tempdb

MODIFY FILE (NAME = temp5, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

ALTER DATABASE tempdb

MODIFY FILE (NAME = temp6, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

ALTER DATABASE tempdb

MODIFY FILE (NAME = temp7, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

ALTER DATABASE tempdb

MODIFY FILE (NAME = temp8, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

-- Log file (templog) — can be different if needed, but we’ll also fix it to 20 GB

ALTER DATABASE tempdb

MODIFY FILE (NAME = templog, SIZE = 20480MB, MAXSIZE = 20480MB, FILEGROWTH = 0);

What is plex? "plex is missing" replacing disk in a mirror [duplicate]

I have replaced a defective drive on mirror in Windows 2016 Server 

1. One disk from the mirror. Disk 1 status: Failed Redundancy, online

2. The new unformatted disk which is supposed to be part of the mirror. Disk 2 dynamic status : online

3. A missing disk

I tried to select the missing disk an choose "Resynchronize mirror" Nothing happened, then I tried "Reactivate volume" and I got "plex is missing"

What is plex and how do I rebuild my mirror?

The solution:

I selected the disk 1 status: Failed Redundancy by right click > choose "Remove Mirror" for the disk labeled missing, next you select the disk which already is in the mirror and choose "add mirror" a dialog box pops up and you choose the new created disk.

This solution resolved the 'plex is missing' error.