Returns one row per authenticated session on SQL Server. sys.dm_exec_sessions is a server-scope view that shows information about all active user connections and internal tasks. This information includes client version, client program name, client login time, login user, current session setting, and more.

sys.dm_exec_sessions is extremely useful DMV when you need to fetch details like login name, transaction isolation level, status, used databases, language etc.

Query 1 : Complete details of every SQL Session

SELECT

S.SESSION_ID,

S.STATUS,

S.HOST_NAME,

DB_NAME(S.DATABASE_ID) DBNAME,

C.CLIENT_NET_ADDRESS,

CASE WHEN S.LOGIN_NAME = S.ORIGINAL_LOGIN_NAME THEN S.LOGIN_NAME ELSE S.LOGIN_NAME + ‘ (‘ +S.ORIGINAL_LOGIN_NAME + ‘)’ END AS LOGIN_NAME,

S.PROGRAM_NAME,

C.CONNECT_TIME, – DIFFRENT BETWEEN CONNECT & LOGIN TIME IS TIME TAKEN BY PRELOGON ACTIVITIES

S.LOGIN_TIME,

CASE S.TRANSACTION_ISOLATION_LEVEL

WHEN 0 THEN ‘UNSPECIFIED’

WHEN 1 THEN ‘READUNCOMITTED’

WHEN 2 THEN ‘READCOMMITTED’

WHEN 3 THEN ‘REPEATABLE’

WHEN 4 THEN ‘SERIALIZABLE’

WHEN 5 THEN ‘SNAPSHOT’

ELSE CAST(S.TRANSACTION_ISOLATION_LEVEL AS VARCHAR(32))

END AS TRANSACTION_ISOLATION_LEVEL_NAME,

–S.LAST_SUCCESSFUL_LOGON, — REQUIRES ‘COMMON CRITERIA COMPLIANCE ENABLED’ OPTION VIA SP_CONFIGURE.

–S.LAST_UNSUCCESSFUL_LOGON, — REQUIRES ‘COMMON CRITERIA COMPLIANCE ENABLED’ OPTION VIA SP_CONFIGURE.

–S.UNSUCCESSFUL_LOGONS, — REQUIRES ‘COMMON CRITERIA COMPLIANCE ENABLED’ OPTION VIA SP_CONFIGURE.

S.CPU_TIME AS CPU_TIME_MS,

S.MEMORY_USAGE AS MEMORY_USAGE_PAGES,

S.ROW_COUNT,

S.PREV_ERROR,

S.LAST_REQUEST_START_TIME,

S.LAST_REQUEST_END_TIME,

C.NET_TRANSPORT,

C.PROTOCOL_TYPE,

S.LANGUAGE,

S.DATE_FORMAT,

ST.TEXT AS QUERY_TEXT

FROM

SYS.DM_EXEC_SESSIONS S

FULL OUTER JOIN SYS.DM_EXEC_CONNECTIONS C ON C.SESSION_ID = S.SESSION_ID

CROSS APPLY SYS.DM_EXEC_SQL_TEXT(C.MOST_RECENT_SQL_HANDLE) ST

WHERE

S.SESSION_ID IS NULL

OR S.SESSION_ID > 50

ORDER BY

S.SESSION_ID

Query 2 :  What number session every login have?

SELECT LOGIN_NAME , COUNT(SESSION_ID) AS [SESSION_COUNT]

FROM SYS.DM_EXEC_SESSIONS

GROUP BY LOGIN_NAME ORDER BY COUNT(SESSION_ID) DESC ;

Remarks

1.       All Possible status of sessions :

·         Running - Currently running one or more requests

·         Sleeping - Currently running no requests

·         Dormant – Session has been reset because of connection pooling and is now in prelogin state.

·         Preconnect - Session is in the Resource Governor classifier.

2.       All possible Transaction isolation level of the session, on basis on integer values :

·         0 = Unspecified

·         1 = ReadUncomitted

·         2 = ReadCommitted

·         3 = Repeatable

·         4 = Serializable

·         5 = Snapshot

3.       Common Criteria Compliance Enabled : If this option in server configuration is enabled, logon statistics are displayed in the following columns. If this option is not enabled, these columns will return null values.

·         last_successful_logon

·         last_unsuccessful_logon

·         unsuccessful_logons

4.       Permissions : User required VIEW SERVER STATE permission on the server to see all executing sessions on the instance of SQL Server, otherwise, the user will see only the current session.

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Reference : Rohit Garg (http://mssqlfun.com/)