You have a SQL database in Microsoft Fabric that uses the default settings for a...

The blocking is caused by an uncommitted explicit transaction in the blocking session that is holding locks. → Yes

While an UPDATE operation on Sales.Orders is occurring, SELECT statements will be blocked. → No

Joining sys.dm_tran_locks to sys.dm_exec_requests will show which session holds locks involved in the blocking chain. → Yes

Comprehensive and Detailed Explanation with all Developing AI-Enabled Database Solutions documents : =

The first statement is Yes . The evidence is conclusive: the blocking session is sleeping , has open_transaction_count = 1 , and its last submitted command was BEGIN TRANSACTION UPDATE Sales.Orders . Microsoft specifically identifies a sleeping session with an open transaction as a classic blocking condition: modifications retain their exclusive locks until the transaction is committed or rolled back . The LCK_M_X waits and identical nonzero blocking_session_id values confirm that other requests are waiting for incompatible exclusive locks.

The second statement is No because READ_COMMITTED_SNAPSHOT is ON by default for SQL database in Microsoft Fabric . Under the default READ COMMITTED isolation level, reads therefore use row versioning rather than shared locks. Consequently, a normal SELECT can read the appropriate committed row version while an UPDATE holds locks, so the writer does not ordinarily block the reader. Microsoft explicitly documents RCSI as ON by default in SQL database in Microsoft Fabric .

The third statement is Yes in the context of blocking diagnostics. sys.dm_tran_locks exposes lock ownership through fields such as request_session_id , request_mode , and request_status , while sys.dm_exec_requests exposes active request and blocking_session_id information. Correlating these DMVs allows you to associate locks with sessions participating in a blocking chain. Microsoft specifically recommends sys.dm_tran_locks for determining which locks are currently held and sys.dm_exec_requests for identifying blocked and blocking sessions.