Active Transactions - How long, Current State, Bytes Reserved/Used, Which DB and What Query ?

SELECT 
CASE dbt.database_id WHEN 32767 THEN 'Resource' ELSE D.name END [DB],
a.session_id [Session],
a.open_transaction_count [Tran. Count],
b.transaction_begin_time [Tran. Started at],
DATEDIFF(SECOND,b.transaction_begin_time,GETDATE()) [Tran. Active(Second(s))],
CHOOSE(b.transaction_type,'Read/write transaction','Read-only transaction','System transaction','Distributed transaction') [Tran. Type],
CHOOSE(b.transaction_state,'The transaction has been initialized but has not started.','The transaction is active.','The transaction has ended. This is used for read-only transactions.','The commit process has been initiated on the distributed transaction. This is for distributed transactions only. The distributed transaction is still active but further processing cannot take place.','The transaction is in a prepared state and waiting resolution.','The transaction has been committed.','The transaction is being rolled back.','The transaction has been rolled back.') [Transaction Sate],
dbt.database_transaction_log_bytes_reserved [Log reserved (Bytes)],
dbt.database_transaction_log_bytes_used [Log used (Bytes)],
x.[text] [Actual Query]
FROM sys.dm_tran_session_transactions a JOIN sys.dm_tran_active_transactions b
ON (a.transaction_id = b.transaction_id)
JOIN sys.dm_exec_connections C ON (a.session_id = C.session_id)
JOIN sys.dm_tran_database_transactions DBT ON(dbt.transaction_id = b.transaction_id)
LEFT JOIN sys.Databases D ON (D.database_id = DBT.database_id) 
CROSS APPLY sys.dm_exec_sql_text(C.most_recent_sql_handle) x 

Failed to update database "DATABASE" because the database is read-only.

The reasone may be any one of the following

1. The database is Read-Only (or)
2. The database is a Snapshot

How to identity whether the database is Read-Only, Snapshot and Source database of the snapshot ?

a) Read-Only:
SELECT DATABASEPROPERTYEX('DatabaseName','Updateability') 'Read Only'
Read Only
READ_ONLY


SELECT Is_Read_Only 'Read Only' FROM SYS.databases WHERE name = 'DatabaseName'
Read Only
1

b) Snapshot source:
SELECT CASE WHEN DB_NAME(source_database_id) IS NULL THEN 'Not a Snapshot' ELSE 'Snapshot Created from ' + '"' + DB_NAME(source_database_id) + '"' END 'Source DB Name' FROM SYS.databases
WHERE name = 'DatabaseName'


If the Database is not a Snapshot
Source DB Name
Not a Snapshot


If the Database is a Snapshot
Source DB Name
Snapshot Created from "SourceDatabaseName"

Note: Snapshot can not be created for Log file:
Log files, offline files, restoring files, and defunct files for database snapshots should not be specified. "Database_log" is not an eligible file for a database snapshot.