If you execute the DBCC CHECKIDENT ('Tablename',reseed,0) in an existing database and a newly created database,the command is behaving totally different way.
Example below
CREATE TABLE Test1
(
Id int identity(1,1) primary key,
name nvarchar(10) )
DELETE FROM Test1
EXEC DBCC CHECKIDENT ('Test1',reseed,0);
INSERT INTO Test1 (name) VALUES('Test')
In the above result system started storing identity from "0" instead of "1"
DELETE FROM Test1
EXEC DBCC CHECKIDENT ('Test1',reseed,0);
INSERT INTO Test1 (name) VALUES('Test')
To correct the issue verify the last value first based on that reseed the data
Declare @lastValue int
SELECT @lastValue = CONVERT(INT,last_value )
FROM sys.identity_columns ic WITH (NOLOCK)
INNER JOIN sys.objects o WITH (NOLOCK) ON ic.OBJECT_ID = o.OBJECT_ID
WHERE o.name = 'Test1'
IF @lastValue IS NOT NULL
EXEC DBCC CHECKIDENT ('Test',reseed,0);
