January 06, 2010

Maximum Capacity Specifications for SQL Server

Maximum Capacity Specifications for SQL Server

The following tables specify the maximum sizes and numbers of various objects defined in SQL Server components.

Database Engine Objects
The following table specifies the maximum sizes and numbers of various objects defined in SQL Server databases or referenced in Transact-SQL statements.

SQL Server Database Engine object Maximum sizes/numbers SQL Server (32-bit) Maximum sizes/numbers SQL Server (64-bit)
Batch size1
65,536 * Network Packet Size
65,536 * Network Packet Size

Bytes per short string column
8,000
8,000

Bytes per GROUP BY, ORDER BY
8,060
8,060

Bytes per index key2
900
900

Bytes per foreign key
900
900

Bytes per primary key
900
900

Bytes per row8
8,060
8,060

Bytes in source text of a stored procedure
Lesser of batch size or 250 MB
Lesser of batch size or 250 MB

Bytes per varchar(max), varbinary(max), xml, text, or image column
2^31-1
2^31-1

Characters per ntext or nvarchar(max) column
2^30-1
2^30-1

Clustered indexes per table
1
1

Columns in GROUP BY, ORDER BY
Limited only by number of bytes
Limited only by number of bytes

Columns or expressions in a GROUP BY WITH CUBE or WITH ROLLUP statement
10
10

Columns per index key7
16
16

Columns per foreign key
16
16

Columns per primary key
16
16

Columns per nonwide table
1,024
1,024

Columns per wide table
30,000
30,000

Columns per SELECT statement
4,096
4,096

Columns per INSERT statement
4096
4096

Connections per client
Maximum value of configured connections
Maximum value of configured connections

Database size
524,272 terabytes
524,272 terabytes

Databases per instance of SQL Server
32,767
32,767

Filegroups per database
32,767
32,767

Files per database
32,767
32,767

File size (data)
16 terabytes
16 terabytes

File size (log)
2 terabytes
2 terabytes

Foreign key table references per table4
253
253

Identifier length (in characters)
128
128

Instances per computer
50 instances on a stand-alone server for all SQL Server editions except for Workgroup. Workgroup supports a maximum of 16 instances per computer.

SQL Server supports 25 instances on a failover cluster.
50 instances on a stand-alone server.

25 instances on a failover cluster.

Length of a string containing SQL statements (batch size)1
65,536 * Network packet size
65,536 * Network packet size

Locks per connection
Maximum locks per server
Maximum locks per server

Locks per instance of SQL Server5
Up to 2,147,483,647
Limited only by memory

Nested stored procedure levels6
32
32

Nested subqueries
32
32

Nested trigger levels
32
32

Nonclustered indexes per table
999
999

Number of distinct expressions in the GROUP BY clause when any of the following are present: CUBE, ROLLUP, GROUPING SETS, WITH CUBE, WITH ROLLUP
32
32

Number of grouping sets generated by operators in the GROUP BY clause
4,096
4,096

Parameters per stored procedure
2,100
2,100

Parameters per user-defined function
2,100
2,100

REFERENCES per table
253
253

Rows per table
Limited by available storage
Limited by available storage

Tables per database3
Limited by number of objects in a database
Limited by number of objects in a database

Partitions per partitioned table or index
1,000
1,000

Statistics on non-indexed columns
30,000
30,000

Tables per SELECT statement
Limited only by available resources
Limited only by available resources

Triggers per table3
Limited by number of objects in a database
Limited by number of objects in a database

Columns per UPDATE statement (Wide Tables)
4096
4096

User connections
32,767
32,767

XML indexes
249
249


1Network Packet Size is the size of the tabular data stream (TDS) packets used to communicate between applications and the relational Database Engine. The default packet size is 4 KB, and is controlled by the network packet size configuration option.

2The maximum number of bytes in any index key cannot exceed 900 in SQL Server. You can define a key using variable-length columns whose maximum sizes add up to more than 900, provided no row is ever inserted with more than 900 bytes of data in those columns. In SQL Server, you can include nonkey columns in a nonclustered index to avoid the maximum index key size of 900 bytes.

3Database objects include objects such as tables, views, stored procedures, user-defined functions, triggers, rules, defaults, and constraints. The sum of the number of all objects in a database cannot exceed 2,147,483,647.

4Although a table can contain an unlimited number of FOREIGN KEY constraints, the recommended maximum is 253. Depending on the hardware configuration hosting SQL Server, specifying additional FOREIGN KEY constraints may be expensive for the query optimizer to process.

5This value is for static lock allocation. Dynamic locks are limited only by memory.

6If a stored procedure accesses more than 8 databases, or more than 2 databases in interleaving, you will receive an error.

7If the table contains one or more XML indexes, the clustering key of the user table is limited to 15 columns because the XML column is added to the clustering key of the primary XML index. In SQL Server, you can include nonkey columns in a nonclustered index to avoid the limitation of a maximum of 16 key columns. For more information, see Index with Included Columns.

8 SQL Server supports row-overflow storage which enables variable length columns to be pushed off-row. Only a 24-byte root is stored in the main record for variable length columns pushed out of row; because of this, the effective row limit is higher than in previous releases of SQL Server. For more information, see the "Row-Overflow Data Exceeding 8 KB" topic in SQL Server Books Online.

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