Function

• A SQL Server LDF file keeps track of each transaction on the database. This includes inserts, edits, deletions and retrievals of the table data. If SQL commands such as an insert fail, or if the data becomes corrupt, the administrator can use the transaction log to revert back to a previous state, saving the business from network downtime.
  
  

Features

• The administrator can open the transaction log file and view the command statements executed against the database. The features shown are who executed the command, the time, the table used and the time at which the command was sent. This helps identify any issues with the database, or if an unauthorized person attempted access to the data.
  
  

Identification

• The LDF file is usually named the same as the database name with the ".ldf" file extension. This is a quick way to identify an LDF file associated with a specific database. For instance, if the database name is "test," then the LDF file is "test.ldf." The LDF file may also sit in the same directory as the MDF file, which is the main database file containing the data.
  
  

Size

• The size of an LDF can grow to several GB. For this reason, database administrators ensure plenty of space is available on the hard drive. SQL Server also provides configurations to help control the size of the LDF file. The LDF and MDF files require several GBs of space, including the backup files.
  
  

Considerations

• Keep LDF files in a safe location. These transactions are a security risk if an unauthorized user is able to obtain a copy. If the LDF file is on the network, password protect the copies and keep it stored in a secure location. Only database administrators should be able to access the files to avoid anyone compromising the security of the data stored in SQL Server.