There was a question in dba.stackexchange.com titled “module_end extended events duration in microseconds?” that I answered and it was Microsecond in that instance.
Later on I questioned myself if the duration is always in Microseconds for extended events. I found, it is a mix of Millisecond, Microsecond and some are unknown meaning famous NULL. I wrote below tsql code to determine which is what.

SELECT p.name package_name,
       o.name event_name,
       c.name event_field,
       DurationUnit= CASE
                         WHEN c.description LIKE '%milli%' 
                         THEN SUBSTRING(c.description, CHARINDEX('milli', c.description),12)
                         WHEN c.description LIKE '%micro%' 
                         THEN SUBSTRING(c.description, CHARINDEX('micro', c.description),12)
                         ELSE NULL
                     END,
       c.type_name field_type,
       c.column_type column_type
FROM sys.dm_xe_objects o
JOIN 

About two years ago, I was working on an update statistics solution for 15 TB OLTP database.   First thing I needed to know, is the status of statistics.   With a google search I landed into this blog post by Erin Stellato (blog | Twitter) from SQLskills. Which gave me a perfect head start.

I expanded that query to add more things in the result set.

• Separate column for schema and object name.
• Statistics ID.
• Is this a temporary statistics (more here) ?
• Column names (I wanted one row per statistics even with more than one column).
• Ability

Last week I blogged about increasing retention of System Health session files. In this post I will show how you can open multiple files at once and work with the data as one set.

If you select multiple System Health extended event files (with extension .xel) and click open each file will open in separate window of SQL Server Management Studio (SSMS).

You can see here 4 files opened in 4 different windows. Now you cannot sort, group, apply filter, export data from all 4 windows as one data set.

For opening all these files in one window …

As per Microsoft’s books online

The system_health session is an Extended Events session that is included by default with SQL Server. This session starts automatically when the SQL Server Database Engine starts, and runs without any noticeable performance effects. The session collects system data that you can use to help troubleshoot performance issues in the Database Engine. Therefore, we recommend that you do not stop or delete the session.

What this article does not tell you is your individual file size is 5 MB and number of maximum rollover file is 4. Meaning you will only get 20 MB of …

I observed this behavior only in following version of SQL Server while using Always On Availability Group feature.

Version: Microsoft SQL Server 2012 (SP3) (KB3072779) – 11.0.6020.0 (X64) Oct 20 2015 15:36:27 Copyright (c) Microsoft Corporation Enterprise Edition: Core-based Licensing (64-bit) on Windows NT 6.3 (Build 9600: )

In this article by David Barbarin similar behavior was also observed in SQL Server 2014 SP2.

Once I update my statistics with fullscan, with in 10~20 seconds some of the statistics on the same table are getting update on secondary with a sample pecent of rows. Meaning my best statistics are being …