Snapper v4.02 and the Snapper launch party video

I have fixed most of the bugs that showed up during the Snapper launch party session and uploaded the new version (v4.02) of Snapper here:

• http://blog.tanelpoder.com/files/scripts/snapper4.sql

I have also uploaded the launch party hacking session video to enkitec.tv:

• http://enkitec.tv/2013/02/18/snapper-v4-beta-launch-video/

I have not updated the snapper documentation yet, but here are the main improvements:

1. RAC support (query remote instance’s sessions performance data via GV$)
2. Manually taken “before” and “after” snapshot support. No need to use DBMS_LOCK to sleep for a certain number of seconds between snapshots
3. Useful averages in the right side of the output (e.g. average bytes sent/received per roundtrip etc). I will keep adding new averages over the coming weeks.

RAC support

I have kept the syntax backwards-compatible, so when you run Snapper like this …

@snapper ash 5 1 user=tanel

… it will still query only local instance’s sessions.

But if you want to measure all tanel’s sessions in let’s say instance #2 only, you can just add @2 to the session filter condition:

@snapper ash 5 1 user=tanel@2

Or if you want all instances then use @*:

@snapper ash 5 1 user=tanel@*

If you want to measure a single session with sid 1234 in instance #2, you can do it in two ways:

@snapper ash 5 1 1234@2

Or use the inst_id,sid tuple syntax:

@snapper ash 5 1 (2,1234)

Note that the brackets are important, as otherwise snapper thinks that you want to measure SID 2 and SID 1234 in the local instance. You can pass multiple inst_id,SID tuples to the snapper though:

@snapper ash 5 1 (2,1234),(4,5678),(3,999)

Snapper still supports the qc= syntax too, to list all sessions started by a PX query coordinator session:

@snapper ash 5 1 qc=1234@*

Note that the qc= syntax is a bit broken/inconsistent right now – what the qc=1234@* means right now is that Snapper looks up the SID 1234 from every instance and lists slave sessions from all instances. If you use qc=1234@2 for example, then Snapper would only look for QC in the instance #2 and any slaves that are also in instance #2 (but with inter-instance parallelism you may have slaves in other instances too). I will fix it in a near-future version.

I will write about the other major features in separate blog entries, but if you want to learn about it now, then grab a beer (or coffe) and watch the latest enkitec.tv show (it’s a bit over 2 hours :-))

P.S. Snapper 4 is still beta! Some queries (like the qc=) one may take a while to run, running dynamic queries with subqueries against GV$ views efficiently is tricky business. This is why I have kept the old snapper v3 (which is more stable and pretty efficient) in the standard (old) snapper address.

Update: If you want to see what Snapper is capable of (it’s about the old version 3), check this document about using Snapper for Oracle performance measurement.