This message appeared in the SQL Server Error Logs , while executing a long running transaction.

The transaction log for database 'database_name' is full. To find out why space in the log cannot be reused, see the log_reuse_wait_desc column in sys.databases

 I executed the statement below, returning ACTIVE_TRANSACTION :

Select log_reuse_wait_desc from sys.databases where name = ‘db_name’

Active transactions force all logs from the start of the transaction to remain active. Efficient starting and closing of transactions assists log truncation , releasing log space for other transactions.

Some tips on keeping transactions short

1)       Return the minimum amount of data

2)       In large batch jobs , commit regularly

3)       Design transactions to be as short as possible

Read More

Factors that can delay Log Truncation – LOG BACKUP

SQL Server - How to find Open Transactions

SQL Server SLEEPING MODE , locks and transactions

MS DTC and sys.dm_tran_active_transactions