Unable to shrink Data File in SQL Server (Taking too much time) - sql-server-2016

Question

I am using :
SQL Server 2016 Standard edition
Windows Server 2012 R2 (Standard)
Database Size: 1.4TB
Used space from the Primary Data File: 587GB
Unused space in a Primary Data File : 852GB
Recovery Model: Simple
I am trying to shrink the Data file to 687GB by using a following Command:
USE [TestDB]
GO
DBCC SHRINKFILE (N'TestDB' , 687017)
GO
And there is no blocking and no other activities are happening on this database.
The above shrink operation is been in the process since last 19hrs and still not completed.
So can anyone tell me what needs to be done at this point of time.
How much time should be taken by this shrink operation?

Answer 1

When shrinking a data file is taking forever then what needs to be done at this point of time?
Well you need to do the following things:
Rebuild Indexes of a database before performing the shrink operation.
If the size of the file is too large for your environment, then try to shrink the file in small chunks.
The another option to resolve this issue which I like is emptying a file.
- EMPTYFILE :
Migrates all data from the specified file to other files in the same filegroup. In other words, EmptyFile will migrate the data from the specified file to other files in the same filegroup. EmptyFile assures you that no new data will be added to the file. The file can be removed by using the ALTER DATABASE statement.
Example: Emptying a file
The following example demonstrates the procedure for emptying a file so that it can be removed from the database. For the purposes of this example, a data file is first created and it is assumed that the file contains data.
USE AdventureWorks2012;
GO
-- Create a data file and assume it contains data.
ALTER DATABASE AdventureWorks2012
ADD FILE (
NAME = Test1data,
FILENAME = 'C:\t1data.mdf',
SIZE = 5MB
);
GO
-- Empty the data file.
DBCC SHRINKFILE (Test1data, EMPTYFILE);
GO
-- Remove the data file from the database.
ALTER DATABASE AdventureWorks2012
REMOVE FILE Test1data;
GO
That was taken straight from BOL.
How much time should be taken by this shrink operation?
DBCC SHRINKFILE
is a single threaded operation and a single threaded operation does not take advantage of multiple CPUs and have no effect about how much RAM is available.
However; rebuilding indexes before running DBCC SHRINKFILE operations, shrinking file operations will take relatively less time.
Rebuilding Index operations takes advantage of multiple CPUs.
You can also check the DBCC SHRINKFILE completion progress by using the following command:
SELECT percent_complete, estimated_completion_time
FROM sys.dm_exec_requests
WHERE session_id = <spid running the shrink>;

Answer 2

Assuming all of your tables have been reindexed, then I find reducing the database in smaller chunks works better. I have created a little procedure which helps me shrink databases, which might be helpful:
CREATE PROCEDURE Shrinkdb #dbname VARCHAR(128) , #targetpercentfree float
AS
CREATE TABLE #dbresults
(dbname VARCHAR(128) ,
Filename VARCHAR(128),
type_desc VARCHAR(32),
CurrentSizeMB FLOAT,
FreeSpaceMB FLOAT,
percentagefree FLOAT)
DECLARE #statement NVARCHAR(MAX)
SET #STATEMENT = '
use ' + #dbname + ' ;
INSERT into #dbresults
SELECT DB_NAME() AS DbName,
name AS FileName,
type_desc,
size/128.0 AS CurrentSizeMB,
size/128.0 - CAST(FILEPROPERTY(name, ''SpaceUsed'') AS INT)/128.0 AS FreeSpaceMB,
0 as percentageFree
FROM sys.database_files
WHERE type IN (0,1)
AND name not LIKE ''%log%'' '
EXECUTE sp_executesql #statement
IF ##ERROR > 0
BEGIN
PRINT #statement
END
UPDATE #dbresults
SET percentageFree = FreeSpaceMB /(FreeSpaceMB + CurrentSizeMB) * 100
DECLARE #filename NVARCHAR(128), #currentsize INT, #targetsize FLOAT, #percentagefree FLOAT, #freespaceMB float
SELECT #filename = [filename],
#currentsize = CurrentSizeMB,
#freespaceMB = freespaceMB,
#percentagefree = percentagefree
FROM #dbresults
SELECT * FROM #dbresults
SET #targetsize = (#currentsize - #freespaceMB) * (1 + #targetpercentfree /100)
select #targetsize as TargetSize
-- target percentage should be 10% free if > 12 then shrink
IF #percentagefree > #targetpercentfree
BEGIN
WHILE 1= 1
BEGIN
-- doing this in 1 gb chunks means that it is much likelier to finish
SET #currentsize = #currentsize -1000
BEGIN
IF #currentsize < #targetsize
BEGIN
BREAK
END
SET #STATEMENT = ' USE ' + #DBNAME + '; DBCC SHRINKFILE ( ' + + '''' + #filename + '''' + ',' + convert(varchar,#currentsize) + ' )'
EXEC sp_executesql #statement
IF ##ERROR > 0
BEGIN
print #statement
END
END
END
END
go
EXECUTE Shrinkdb #dbname = 'databasename', #targetpercentfree = 5