Category: Linux

Kellyn Pot’vin-Gorman contrasts SQL Server versus Oracle outputs when running a couple common Linux process commands:

In our Oracle environment, we can see every background process, with it’s own pid and along with the process monitor, (pmon)db writer, (dbwr), log writer, (lgwr), we also have archiving, (arcx), job processing, (j00x) performance and other background processing.  I didn’t even grep for the Oracle executable, so you recognize how quickly we can see what is running.

In the SQL Server environment, we only have two processes- our parent process is PID 7 and the child is 9 for SQL Server and nothing to distinguish what they actually are doing.  If we decide to use the pmap utility to view what the parent and child process aredoing, we see only sqlservr as the mapping information.

I imagine that things like this will improve over time for SQL Server, but Oracle definitely has a leg up in this regard.

Anthony Nocentino explains Linux error codes and systemd behavior for SQL on Linux:

Now in the output above, you’ll notice a bolded line. In there, you can system that systemd[1] receives a return code from SQL Server of status=1/FAILURE.  Systemd[1] is the parent process to sqlservr, in fact it’s the parent to all processes on our system. It receives the exit code and immediately, systemd initiates a restart of the service due to the configuration we have for our mysql-server systemd unit.

What’s interesting is that this happens even on a normal shutdown. But that simply doesn’t make sense, return values on clean exits should return 0. It’s my understanding of the SHUTDOWN command, that it will cause the database engine to shutdown cleanly.

On the development side, there aren’t many differences between SQL on Linux versus SQL on Windows (aside from things which haven’t yet made the move); on the administration side, there are some interesting differences.

Anthony Nocentino explains how SQL Server on Linux reacts to memory pressure:

We can use tools like ps, top and htop to look our are virtual and physical memory allocations. We can also look in the /proc virtual file system for our process and look at the status file. In here we’ll find the point in time status of a process, and most importantly the types of memory allocations for a process. We’ll get granular data on the virtual memory allocations and also the resident set size of the process. Here are the interesting values in the status file we’re going to focus on today.

• VmSize – total current virtual address space of the process

• VmRSS – total amount of physical memory currently allocated to the process

• VmSwap – total amount of virtual memory currently paged out to the swap file (disk)

The differences are going to be interesting for people to troubleshoot later, particularly if you look at SOS_SCHEDULER_YIELD and give a knee-jerk reaction that the problem is with CPU.