Reorganize all indexes in a Database in SQL Server.

Index Maintenance is one of the major task for a DBA. If rate of Index fragmentation increased then index de-fragmentation is become required. So we can use index reorganize option to rebuild all the indexes. Use Index reorganize option when rate of index fragmentation is b/w 10% to  40%.

Syntax:

Alter Index All On Table_Name Reorganize.

Example:

ALTER INDEX ALL ON geographicals Reorganize

GO

 

Rebuild Index for All tablex in database:

Exec sp_msforeachtable 'ALTER INDEX ALL ON ? Reorganize'

GO

Reference: 

SQL SERVER – Drop All the Foreign Key Constraint in Database – Create All the Foreign Key Constraint in Database

SET NOCOUNT ON

DECLARE @table TABLE (
 RowId INT PRIMARY KEY IDENTITY(1, 1)
 ,ForeignKeyConstraintName NVARCHAR(200)
 ,ForeignKeyConstraintTableSchema NVARCHAR(200)
 ,ForeignKeyConstraintTableName NVARCHAR(200)
 ,ForeignKeyConstraintColumnName NVARCHAR(200)
 ,PrimaryKeyConstraintName NVARCHAR(200)
 ,PrimaryKeyConstraintTableSchema NVARCHAR(200)
 ,PrimaryKeyConstraintTableName NVARCHAR(200)
 ,PrimaryKeyConstraintColumnName NVARCHAR(200)
 )

INSERT INTO @table (
 ForeignKeyConstraintName
 ,ForeignKeyConstraintTableSchema
 ,ForeignKeyConstraintTableName
 ,ForeignKeyConstraintColumnName
 )
SELECT U.CONSTRAINT_NAME
 ,U.TABLE_SCHEMA
 ,U.TABLE_NAME
 ,U.COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE U
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS C ON U.CONSTRAINT_NAME = C.CONSTRAINT_NAME
WHERE C.CONSTRAINT_TYPE = 'FOREIGN KEY'

UPDATE @table
SET PrimaryKeyConstraintName = UNIQUE_CONSTRAINT_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS R ON T.ForeignKeyConstraintName = R.CONSTRAINT_NAME

UPDATE @table
SET PrimaryKeyConstraintTableSchema = TABLE_SCHEMA
 ,PrimaryKeyConstraintTableName = TABLE_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS C ON T.PrimaryKeyConstraintName = C.CONSTRAINT_NAME

UPDATE @table
SET PrimaryKeyConstraintColumnName = COLUMN_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE U ON T.PrimaryKeyConstraintName = U.CONSTRAINT_NAME

--SELECT * FROM @table
--DROP CONSTRAINT:
SELECT '
ALTER TABLE [' + ForeignKeyConstraintTableSchema + '].[' + ForeignKeyConstraintTableName + ']
DROP CONSTRAINT ' + ForeignKeyConstraintName + '
 
GO'
FROM @table

--ADD CONSTRAINT:
SELECT '
ALTER TABLE [' + ForeignKeyConstraintTableSchema + '].[' + ForeignKeyConstraintTableName + ']
ADD CONSTRAINT ' + ForeignKeyConstraintName + ' FOREIGN KEY(' + ForeignKeyConstraintColumnName + ') REFERENCES [' + PrimaryKeyConstraintTableSchema + '].[' + PrimaryKeyConstraintTableName + '](' + PrimaryKeyConstraintColumnName + ')
 
GO'
FROM @table
GO






Reference:https://blog.sqlauthority.com/2014/04/11/sql-server-drop-all-the-foreign-key-constraint-in-database-create-all-the-foreign-key-constraint-in-database/

List all Orphan users in a SQL Server database

CREATE TABLE ##ORPHANUSER (
DBNAME VARCHAR(100)
,USERNAME VARCHAR(100)
,CREATEDATE VARCHAR(100)
,USERTYPE VARCHAR(100)
)
EXEC SP_MSFOREACHDB ' USE [?]
INSERT INTO ##ORPHANUSER
SELECT DB_NAME() DBNAME, NAME,CREATEDATE,
(CASE 
WHEN ISNTGROUP = 0 AND ISNTUSER = 0 THEN ''SQL LOGIN''
WHEN ISNTGROUP = 1 THEN ''NT GROUP''
WHEN ISNTGROUP = 0 AND ISNTUSER = 1 THEN ''NT LOGIN''
END) [LOGIN TYPE] FROM sys.sysusers
WHERE SID IS NOT NULL AND SID <> 0X0 AND ISLOGIN =1 AND
SID NOT IN (SELECT SID FROM sys.syslogins)'
SELECT *
FROM ##ORPHANUSER
DROP TABLE ##ORPHANUSER

Space occupied by each Schema in SQL Server database

SELECT  SCHEMA_NAME(so.schema_id) AS SchemaName
               ,SUM(ps.reserved_page_count) * 8.0 / 1024 AS SizeInMB
        FROM    sys.dm_db_partition_stats ps
        JOIN    sys.indexes i
          ON    i.object_id                                     =           ps.object_id
         AND    i.index_id                                      =           ps.index_id
JOIN sys.objects so
  ON i.object_id = so.object_id
       WHERE    so.type = 'U'
    GROUP BY so.schema_id
    ORDER BY OBJECT_SCHEMA_NAME(so.schema_id), SizeInMB DESC

T SQL query to find when was the database backed up lastly on SQL Server

Select database_name As [Database Name]
, [name] As [Backup Name]
, Case When Type = 'D' Then 'Full Backup'
When Type = 'I' Then 'Differential Backup'
When Type = 'L' Then 'Log Backup'
Else 'File or filegroup or partial'
End As [Backup Type]
, Recovery_Model
, [backup_start_date] As [Time of the SQL Backup Job]
FROM [msdb].[dbo].[backupset]

SQL Script to find all Date/time columns in database

select
    so.name table_name
   ,sc.name column_name
   ,st.name data_type
from sysobjects so
inner join syscolumns sc on (so.id = sc.id)
inner join systypes st on (st.type = sc.type)
where so.type = 'U'
and st.name IN ('DATETIME', 'DATE', 'TIME')

Generate Script of All indexes in a SQL Server database

SELECT ' CREATE ' +
       CASE
            WHEN I.is_unique = 1 THEN ' UNIQUE '
            ELSE ''
       END +
       I.type_desc COLLATE DATABASE_DEFAULT + ' INDEX ' +
       I.name + ' ON ' +
       SCHEMA_NAME(T.schema_id) + '.' + T.name + ' ( ' +
       KeyColumns + ' )  ' +
       ISNULL(' INCLUDE (' + IncludedColumns + ' ) ', '') +
       ISNULL(' WHERE  ' + I.filter_definition, '') + ' WITH ( ' +
       CASE
            WHEN I.is_padded = 1 THEN ' PAD_INDEX = ON '
            ELSE ' PAD_INDEX = OFF '
       END + ',' +
       'FILLFACTOR = ' + CONVERT(
           CHAR(5),
           CASE
                WHEN I.fill_factor = 0 THEN 100
                ELSE I.fill_factor
           END
       ) + ',' +
       -- default value
       'SORT_IN_TEMPDB = OFF ' + ',' +
       CASE
            WHEN I.ignore_dup_key = 1 THEN ' IGNORE_DUP_KEY = ON '
            ELSE ' IGNORE_DUP_KEY = OFF '
       END + ',' +
       CASE
            WHEN ST.no_recompute = 0 THEN ' STATISTICS_NORECOMPUTE = OFF '
            ELSE ' STATISTICS_NORECOMPUTE = ON '
       END + ',' +
       ' ONLINE = OFF ' + ',' +
       CASE
            WHEN I.allow_row_locks = 1 THEN ' ALLOW_ROW_LOCKS = ON '
            ELSE ' ALLOW_ROW_LOCKS = OFF '
       END + ',' +
       CASE
            WHEN I.allow_page_locks = 1 THEN ' ALLOW_PAGE_LOCKS = ON '
            ELSE ' ALLOW_PAGE_LOCKS = OFF '
       END + ' ) ON [' +
       DS.name + ' ] ' +  CHAR(13) + CHAR(10) + ' GO' [CreateIndexScript]
FROM   sys.indexes I
       JOIN sys.tables T
            ON  T.object_id = I.object_id
       JOIN sys.sysindexes SI
            ON  I.object_id = SI.id
            AND I.index_id = SI.indid
       JOIN (
                SELECT *
                FROM   (
                           SELECT IC2.object_id,
                                  IC2.index_id,
                                  STUFF(
                                      (
                                          SELECT ' , ' + C.name + CASE
                                                                       WHEN MAX(CONVERT(INT, IC1.is_descending_key))
                                                                            = 1 THEN
                                                                            ' DESC '
                                                                       ELSE
                                                                            ' ASC '
                                                                  END
                                          FROM   sys.index_columns IC1
                                                 JOIN sys.columns C
                                                      ON  C.object_id = IC1.object_id
                                                      AND C.column_id = IC1.column_id
                                                      AND IC1.is_included_column =
                                                          0
                                          WHERE  IC1.object_id = IC2.object_id
                                                 AND IC1.index_id = IC2.index_id
                                          GROUP BY
                                                 IC1.object_id,
                                                 C.name,
                                                 index_id
                                          ORDER BY
                                                 MAX(IC1.key_ordinal)
                                                 FOR XML PATH('')
                                      ),
                                      1,
                                      2,
                                      ''
                                  ) KeyColumns
                           FROM   sys.index_columns IC2
                                  --WHERE IC2.Object_id = object_id('Person.Address') --Comment for all tables
                           GROUP BY
                                  IC2.object_id,
                                  IC2.index_id
                       ) tmp3
            )tmp4
            ON  I.object_id = tmp4.object_id
            AND I.Index_id = tmp4.index_id
       JOIN sys.stats ST
            ON  ST.object_id = I.object_id
            AND ST.stats_id = I.index_id
       JOIN sys.data_spaces DS
            ON  I.data_space_id = DS.data_space_id
       JOIN sys.filegroups FG
            ON  I.data_space_id = FG.data_space_id
       LEFT JOIN (
                SELECT *
                FROM   (
                           SELECT IC2.object_id,
                                  IC2.index_id,
                                  STUFF(
                                      (
                                          SELECT ' , ' + C.name
                                          FROM   sys.index_columns IC1
                                                 JOIN sys.columns C
                                                      ON  C.object_id = IC1.object_id
                                                      AND C.column_id = IC1.column_id
                                                      AND IC1.is_included_column =
                                                          1
                                          WHERE  IC1.object_id = IC2.object_id
                                                 AND IC1.index_id = IC2.index_id
                                          GROUP BY
                                                 IC1.object_id,
                                                 C.name,
                                                 index_id
                                                 FOR XML PATH('')
                                      ),
                                      1,
                                      2,
                                      ''
                                  ) IncludedColumns
                           FROM   sys.index_columns IC2
                                  --WHERE IC2.Object_id = object_id('Person.Address') --Comment for all tables
                           GROUP BY
                                  IC2.object_id,
                                  IC2.index_id
                       ) tmp1
                WHERE  IncludedColumns IS NOT NULL
            ) tmp2
            ON  tmp2.object_id = I.object_id
            AND tmp2.index_id = I.index_id
WHERE  I.is_primary_key = 0
       AND I.is_unique_constraint = 0
           --AND I.Object_id = object_id('Person.Address') --Comment for all tables
           --AND I.name = 'IX_Address_PostalCode' --comment for all indexes 

Difference between Detaching database and bringing database Offline

SQL Server Offline and Detach Database




Detach Database/Attach Database: The data and transaction log files of a database can be detached and then reattached to the same or another instance of SQL Server. Detaching and attaching a database is useful if you want to change the database to a different instance of SQL Server on the same computer or to move the database.
Detaching a database removes it from the instance of SQL Server but leaves the database intact within its data files and transaction log files. These files can then be used to attach the database to any instance of SQL Server, including the server from which the database was detached.

you can attach a copied or detached SQL Server database. When you attach a SQL Server 2005 database that contains full-text catalog files onto a SQL Server 2016 server instance, the catalog files are attached from their previous location along with the other database files, the same as in SQL Server When you attach a database, all data files (MDF and NDF files) must be available. If any data file has a different path from when the database was first created or last attached, you must specify the current path of the file.

The requirement for attaching log files depends partly on whether the database is read-write or read-only, as follows:

• For a read-write database, you can usually attach a log file in a new location. However, in some cases, reattaching a database requires its existing log files. Therefore, it is important to always keep all the detached log files until the database has been successfully attached without them.
  If a read-write database has a single log file and you do not specify a new location for the log file, the attach operation looks in the old location for the file. If it is found, the old log file is used, regardless of whether the database was shut down cleanly. However, if the old log file is not found and if the database was shut down cleanly and has no active log chain, the attach operation attempts to build a new log file for the database.
• If the primary data file being attached is read-only, the Database Engine assumes that the database is read-only. For a read-only database, the log file or files must be available at the location specified in the primary file of the database. A new log file cannot be built because SQL Server cannot update the log location stored in the primary file.

Database Offline: Database is unavailable. A database becomes offline by explicit user action and remains offline until additional user action is taken. For example, the database may be taken offline in order to move a file to a new disk. The database is then brought back online after the move has been completed.


Use OFFLINE and ONLINE
1) If you are trying to make the database temporary unavailable for a period of time, you could take the database OFFLINE, and make it available by bringing it ONLINE whenever it is or you are ready.

2a) If you want to move the database or log files to different physical location or changing the database and/or log physical file name, AND keep them within the same SQL Server instance.
- Before you take the database offline, you need to know the logical name of the file. The name field is the logical name for the physical file name that you are about to change the path. Record the logical name for later use.

SELECT name, type, type_desc, physical_name, state, state_desc
FROM sys.master_files
WHERE database_id = DB_ID('YourDatabase')

- Take the database OFFLINE.
ALTER DATABASE YourDatabase SET OFFLINE
WITH ROLLBACK IMMEDIATE;

-Move the database and/or log files to different location.
- Update the database and/or log files path registered on its SQL Server instance. Execute the T-SQL command for each database and log files,

ALTER DATABASE YourDatabase 
MODIFY FILE (NAME = YourFileLogicalName,
FILENAME = 'Your Database or Log new physical path')

Bring the database ONLINE.
ALTER DATABASE YourDatabase SET ONLINE;

If you just want to change the logical name, you dont have to take the database OFFLINE. You could change it on SSMS or T-SQL.

Right click on the database > Properties > Select Page > Change it under Logical Name column > OK.

ALTER DATABASE YourDatabase 
MODIFY FILE (NAME = YourFileLogicalName,
NEWNAME = YourFileNewLogicalName)

2b) If you are relocating a file during part of the scheduled disk maintenance process, you may need to change the file path registered on its SQL Server instance before taking the database OFFLINE. This assure the server has the right path for the database and log files when the instance restart, after being shut down for maintenance.
- When the database and/or log file path is successfully updated on the instance, a message will show; 'The file "YourDatabaseFile" has been modified in the system catalog. The new path will be used the next time the database is started.'

Use DETACH and ATTACH,
1) If you want to move the database and log files to a different SQL Server instance or another server.
- Rollback active transaction and gain exclusive access. Detach the database. (optional: update statistics) 

ALTER DATABASE YourDatabase SET SINGLE_USER
WITH ROLLBACK IMMEDIATE;

EXEC sp_detach_db 'YourDatabase', 'true'

- Move database and log files to different location.
- Attach the database on different instance on same/another server. 

USE master;

CREATE DATABASE YourDatabase
ON (FILENAME = 'the physical path of your database file')
LOG ON (FILENAME = 'the physical path of your log file')
FOR ATTACH;

- If the database has previously set to single user, you may want to set it to multiple user access option.

ALTER DATABASE YourDatabase SET MULTI_USER

2) Even though you can choose to detach and attach the database back on the same SQL Server instance for scenario like changing physical path or file name, it is recommended to use the OFFLINE and ONLINE methods due to the restriction and limitation on DETACH. When you detach a database, you remove the database from the instance. It is required to remove the database from any participation of replication, mirroring and snapshot.

Reference: 

Query to List all the partitioned tables in SQL Server database

select object_schema_name(i.object_id) as [schema],
    object_name(i.object_id) as [object],
    i.name as [index],
    s.name as [partition_scheme]
    from sys.indexes i
    join sys.partition_schemes s on i.data_space_id = s.data_space_id order by [schema]

T-SQL code to get the active Connections for each Database.

--Method 1

 SELECT 

    DB_NAME(dbid) as DBName, 

    COUNT(dbid) as NoOfConnections,

    loginame as LoginName

FROM

    sys.sysprocesses

WHERE 

    dbid > 0

GROUP BY 

    dbid, loginame

--Method 2

EXEC sp_who2

--Method 3

SELECT  spid,

        sp.[status],

        loginame [Login],

        hostname, 

        blocked BlkBy,

        sd.name DBName, 

        cmd Command,

        cpu CPUTime,

        physical_io DiskIO,

        last_batch LastBatch,

        [program_name] ProgramName   

FROM master.dbo.sysprocesses sp 

JOIN master.dbo.sysdatabases sd ON sp.dbid = sd.dbid

ORDER BY DBName,spid

Delete all Tables based on creation date

--Delete all Tables based on creation date



 DECLARE @tname VARCHAR(100)
DECLARE @sql VARCHAR(max)

DECLARE db_cursor CURSOR FOR
SELECT name AS tname
FROM sys.objects
WHERE create_date < GETDATE() - 1-- Days old

OPEN db_cursor
FETCH NEXT FROM db_cursor INTO @tname

WHILE @@FETCH_STATUS = 0
BEGIN
       SET @sql = 'DROP TABLE ' + @tname
       --EXEC (@sql)  -- For Executing
       PRINT @sql --For Printing

       FETCH NEXT FROM db_cursor INTO @tname
END

CLOSE db_cursor
DEALLOCATE db_cursor

Simplest way to Truncate/Delete all tables in a given database.

Simplest way to Truncate all tables in a given database.

Use databasename

EXEC sp_MSForEachTable 'Truncate TABLE ?' --- For Truncating all tables

Simplest way to Truncate all tables in a given database.

Use databasename

EXEC sp_MSforeachtable @command1 = "DROP TABLE ?"  --- For Deleting all tables

Database cannot be opened due to inaccessible files or insufficient memory or disk space

Database cannot be opened due to inaccessible files or insufficient memory or disk space

Msg 945, Level 14, State 2, Line 1

Database 'db' cannot be opened due to inaccessible files or insufficient memory or disk space. See the SQL Server errorlog for details.

Solution:

Check Microsoft SQL Server error log and determine reason for the cause.

If it is because of a persistent I/O error related to Application Programming Interface, a torn page, or other hardware issues, resolved it and restore it with help of backup. But if there is no availability of backups then try DBCC CHECKDB repair option.

 If possible add some disk space to files drive or cleanup some disk space.

Verify the permissions of user account.

Verify if the database is property is set to AutoGrow On.

.mdf and .ldf files should not be marked as Read Only on windows level.

If none of the above solved Issue: Try this

1. Change the database to offline to clear the db status

use master

alter database dbname set offline

2. Now change the database to online, at this step log file and data files will be verified by sql server

use master

alter database dbname set online

Checklist for Restoring TDE Encrypted database on different SQL Server

In order to perform a successful restore, we'll need the database master key in the master database in place and we'll need to restore the certificate used to encrypt the database, but we'll need to make sure we restore it with the private key. In checklist form:

• There's a database master key in the master database.
• The certificate used to encrypt the database is restored along with its private key.
• The database backup to be restored.

How to find percentage of a database backup job done in SQL Server?

Script to find percentage of a database backup job is done

SELECT percent_complete
 ,*
FROM sys.dm_exec_requests
WHERE command IN (
  'RESTORE DATABASE'
  ,'BACKUP DATABASE'
  )

Elapsed time in Hours to complete the Job

SELECT command
 ,percent_complete
 ,'elapsed' = total_elapsed_time / 3600000.0
 ,'remaining' = estimated_completion_time / 3600000.0
FROM sys.dm_exec_requests
WHERE command LIKE 'BACKUP%'

DBCC CHECKDB :A database snapshot cannot be created because it failed to start.

Disk space issues during DBCC CHECKDB

Sometimes an issue arises when the hidden database snapshot runs out of space. Because it’s implemented using alternate streams of the existing data files, the database snapshot consumes space from the same location as the existing data files. If the database being checked has a heavy update workload, more and more pages are pushed into the database snapshot, causing it to grow. In a situation where the volumes hosting the database don’t have much space, this can mean the hidden database snapshot runs out of space and DBCC CHECKDB stops with an error. An example of this is shown here (the errors can vary depending on the exact point at which the database snapshot runs out of space):

DBCC CHECKDB ('SalesDB2') WITH NO_INFOMSGS, ALL_ERRORMSGS;
GO
Msg 1823, Level 16, State 1, Line 5
A database snapshot cannot be created because it failed to start.
Msg 1823, Level 16, State 2, Line 1
A database snapshot cannot be created because it failed to start.
Msg 7928, Level 16, State 1, Line 1
The database snapshot for online checks could not be created. Either the reason is given in a previous error or one of the underlying volumes does not support sparse files or alternate streams. Attempting to get exclusive access to run checks offline.
Msg 5128, Level 17, State 2, Line 1
Write to sparse file 'C:\SQLskills\SalesDBData.mdf:MSSQL_DBCC20' failed due to lack of disk space.
Msg 3313, Level 21, State 2, Line 1
During redoing of a logged operation in database 'SalesDB2', an error occurred at log record ID (1628:252:1). Typically, the specific failure is previously logged as an error in the Windows Event Log service. Restore the database from a full backup, or repair the database.
Msg 0, Level 20, State 0, Line 0
A severe error occurred on the current command. The results, if any, should be discarded.

In this case, the solution is to create your own database snapshot, placing the snapshot files on a volume with more disk space, and then to run DBCC CHECKDB on that. DBCC CHECKDB recognizes that it’s already running on a database snapshot and doesn’t attempt to create another one. If a database snapshot was created by DBCC CHECKDB, it’s discarded automatically after the consistency-checking algorithms are complete.
While it runs, DBCC CHECKDB creates a database snapshot (if needed) and suspends the FILESTREAM garbage collection process. You might notice garbage collection run at the start of the consistency checking process; the creation of the hidden database snapshot starts with a checkpoint, which is what triggers FILESTREAM garbage collection. The suspension of garbage collection activity allows the consistency-checking algorithms to see a transactionally consistent view of the FILESTREAM data on any FILESTREAM data containers

Alternatives to using a database snapshot

A database snapshot isn’t required under the following conditions.

• The specified database is a database snapshot itself.
• The specified database is read-only, in single-user mode, or in emergency mode.
• The server was started in single-user mode with the –m command-line option.

In these cases, the database is already essentially consistent because no other active connections can be making changes that would break the consistency checks.
A database snapshot can’t be created under the following conditions.

• The specified database is stored on a non–NTFS file system, in which case a database snapshot can’t be created because it relies on NTFS sparse-file technology.
• The specified database is tempdb, because a database snapshot can’t be created on tempdb.
• The TABLOCK option was specified.

If a database snapshot can’t be created for any reason, DBCC CHECKDB attempts to use locks to obtain a transactionally consistent view of the database. First, it obtains a database-level exclusive lock so that it can perform the allocation consistency checks without any changes taking place. Offline consistency checks can’t be run on master or on tempdb because these databases can’t be exclusively locked. This means that allocation consistency checks are always skipped for tempdb (as was usually the case with SQL Server 2000, too). This also isn’t possible if the database is an Availability Group replica, in which case error 7934 is reported if the database snapshot creation fails.
Rather than wait for the exclusive lock indefinitely (or whatever the server lock timeout period has been set to), DBCC CHECKDB waits for 20 seconds (or the configured lock timeout value for the session) and then exits with the following error:

DBCC CHECKDB ('msdb') WITH TABLOCK;
GO
Msg 5030, Level 16, State 12, Line 1
The database could not be exclusively locked to perform the operation.
Msg 7926, Level 16, State 1, Line 1
Check statement aborted. The database could not be checked as a database snapshot could not be created and the database or table could not be locked. See Books Online for details of when this behavior is expected and what workarounds exist. Also see previous errors for more details.

If the lock was acquired after the allocation checks are completed, the exclusive lock is dropped and table-level share locks are acquired while the table-level logical consistency checks are performed. The same time-out applies to these table-level locks.
One way or another, DBCC CHECKDB obtains a transactionally consistent view of the database that it’s checking. After that, it can start processing the database.





Reference:Microsoft SQL Server 2012 Internals