sp_set_session_context (Transact-SQL)
Applies to: 
SQL Server 2016 (13.x) and later
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
SQL analytics endpoint in Microsoft Fabric
Warehouse in Microsoft Fabric
Sets a key-value pair in the session context.
Transact-SQL syntax conventions
Syntax
sp_set_session_context
[ @key = ] N'key'
, [ @value = ] 'value'
[ , [ @read_only = ] read_only ]
[ ; ]
Arguments
[ @key = ] N'key'
The key being set. @key is sysname with no default. The maximum key size is 128 bytes.
[ @value = ] 'value'
The value for the specified key. @value is sql_variant, with a default of NULL. Setting a value of NULL frees the memory. The maximum size is 8,000 bytes.
[ @read_only = ] read_only
A flag indicating whether the specified key can be changed on the logical connection. @read_only is bit with a default of 0.
- If
1, the value for the specified key can't be changed again on this logical connection. - If
0, the value can be changed.
Permissions
Any user can set a session context for their session.
Remarks
Like other stored procedures, only literals and variables (not expressions or function calls) can be passed as parameters.
The total size of the session context is limited to 1 MB. If you set a value that causes this limit to be exceeded, the statement fails. You can monitor overall memory usage in sys.dm_os_memory_objects.
You can monitor overall memory usage by querying sys.dm_os_memory_cache_counters as follows:
SELECT * FROM sys.dm_os_memory_cache_counters WHERE type = 'CACHESTORE_SESSION_CONTEXT';
Examples
A. Set and return a session context
The following example shows how to set and then return a session's context key named language, with a value of English.
EXEC sys.sp_set_session_context @key = N'language', @value = 'English';
SELECT SESSION_CONTEXT(N'language');
The following example demonstrates the use of the optional read-only flag.
EXEC sys.sp_set_session_context @key = N'user_id', @value = 4, @read_only = 1;
B. Set and return a client correlation ID
The following example shows how to set and retrieve a session context key named client_correlation_id, with a value of 12323ad.
Set the value.
EXEC sp_set_session_context 'client_correlation_id', '12323ad';Retrieve the value.
SELECT SESSION_CONTEXT(N'client_correlation_id');