What is the simplest/quickest way to detect that Journaling was switched to a new file?

Hi Alexey.

I'm not aware of such event handler.

However, I wonder why do you need it at all? If you provide use case, perhaps we can advice some other way to achieve it.

Ignoring whether there is a %SYSTEMJournal:IsPrimary() or some such (I simply don't know). If primary and alternate are on their own separate disk devices (dev/sdj/pri_journals) you will see writes only on one of them. Not very bulletproof but depends on what you are looking for.

If you want to detect a journal change, it means, you want to do something, when such a change took place.

I think, you could do something like this:

a) Start a process at system start (for example, from %ZSTART), which will handle journal changes
b) In that process, get the current journal file
c) try to open this file
d) if (c) fails, wait a few seconds and then goto c)
e) if (c) succeds,  handle journal file change, then goto b)
   
A simplified routine, but untested (as a suggestion):

journalchanges ; Handle journal file changes

#define SWITCHES $system.Util.GetSwitch()
#define SHUTDOWN ##Expression(2**16)
#define BITAND(%a,%b) $zboolean(%a,%b,1)
   
   set jouFile=$$getCurrentFile()  // get the current journal file
   if jouFile="" Quit              // should not happen, but who knows...
   
   while '$$$BITAND($$$SWITCHES, $$$SHUTDOWN) { // stop, if shutdown is in progress
      open jouFile:"WL":1 // try to get ownership
      continue:'$test     // locked (by the journaling system), we try once again
      close jouFile       // because we were interested in status only
   
      // Now you can use <jouFile> to handle the file change
      // By now, he journaling system uses a new journal file
      
      set jouFile=$$getCurrentFile() // get the new journal file
      if jouFile = "" quit           // just to be on the safe side
   }
   
   quit  // we are done
   
    
getCurrentFile()
{
   try { return ##class(%SYS.Journal.System).GetCurrentFile().Name } catch { return "" }
}

I'm not sure if this is the simplest or the quickest, but if your licensing includes the ability of creating an Ensemble Production (that's the 2012 term, anyway - we've not yet upgraded to HealthShare or Iris) you could create a pair of Services based on the EnsLib.File.PassthroughService - one for the primary and one for the secondary journaling directories. Each service will scan the directory (it's configurable how often with the Call Interval parameter) and you can fire a Business Process or Operation when the new file hits. You can even set up a File Specification to make sure that if someone manually puts a file in one of the directories that the process may not 'fire' if it's not supposed to.

You could even have different rules for each process - for example, if the Secondary Journaling directory gets a new file created in it, the Business Process could have a rule to fire off an email to the system administrator(s) warning that the drive housing the primary journaling directory may be full or compromised in some way.

Hope this helps!