Performance is slow when you open and read event files (.xel) by using XEvent Linq reader in Microsoft SQL Server 2012 or SQL Server 2014.
Service pack information
This problem requires a client fix, not a SQL Server engine fix.
Note This change doesn't affect sys.fn_xe_file_target_read_file.
To resolve this problem, get Service Pack 3 (SP3) for SQL Server 2012.
For more information about SQL Server 2012 SP3, see bugs that are fixed in SQL Server 2012 Service Pack 3.
Cumulative Update information
The issue was first fixed in the following cumulative update of SQL Server.
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.