Log level is not always a good indicator of how big a deal what is being logged is.
For example:
2 [Generic.Event] Unable to allocate shared memory minimum - this error prevents startup so critical
1 [Generic.Event] MirrorServer: Lost ReadDmn (ACK) connection to async - loss of connection connection to a mirror doesn't rate as even a warning?

Any maximum you set less than free space on the filesystem will just hit the limit sooner.
The instance could use more RAM in the global buffer and maybe more filesystem space.
You should look at this and this.

 I would expect the WIJ to close to force it to the disk about every 80 seconds ie every write cycle.

my quick testing:

$while true; do
> ls -l IRIS.WIJ | cut -f 10-13 -d ' '
> sleep 40
> done
Oct 26 12:26 IRIS.WIJ
Oct 26 12:27 IRIS.WIJ
Oct 26 12:27 IRIS.WIJ
Oct 26 12:28 IRIS.WIJ
Oct 26 12:28 IRIS.WIJ
Oct 26 12:30 IRIS.WIJ
Oct 26 12:30 IRIS.WIJ
Oct 26 12:31 IRIS.WIJ
Oct 26 12:31 IRIS.WIJ
Oct 26 12:32 IRIS.WIJ
Oct 26 12:32 IRIS.WIJ
Oct 26 12:34 IRIS.WIJ
Oct 26 12:34 IRIS.WIJ
Oct 26 12:35 IRIS.WIJ
Oct 26 12:35 IRIS.WIJ
Oct 26 12:36 IRIS.WIJ

You should look at this - Write Image Journaling and Recovery

The WIJ can live in other places.

As a guess the the web page is not getting data updates.
What does ^MIRROR say is happening?

Have you checked if there are firewalls interfering?

So testing shows the old way was better in this case.

Failure
iris session ${INST} -U %sys << EOF

w "stopping the mirror 1 is sucess: " zw ##class(SYS.Mirror).StopMirror("MIRROR")

h

EOF

%SYS>

%SYS>
stopping the mirror 1 is sucess: "0 "_$lb($lb(2050,,,,,,,,,$lb(,"%SYS",$lb("e^Shutdown+7^MIRRORMGR^2","e^zStopMirror+4^SYS.Mirror.1^1","e^^^0"))))/* ERROR #2050: Mirror configuration not loaded */

%SYS>
Sucess
$ iris session ${INST} -U %sys << EOF
>
> zw ##class(SYS.Mirror).StopMirror("MIRROR")                                  <
> h
> EOF


%SYS>

%SYS>
stopping the mirror 1 is sucess: 1

%SYS>

Same either way :(
iris session ${INST} -U %sys '##class(SYS.Mirror).StopMirror("MIRROR")' ;echo $?
0

Thanks for this example.
I had used:

iris session ${INST} -U %sys << EOF

w "stopping the mirror 1 is sucess: " zw ##class(SYS.Mirror).StopMirror("PMIR") h
EOF

The only way to get an estimate I can think of is running the compact against a SAN snapshot on similar hardware.
The free blocks could be anywhere in the file and that plays a big role.

Here are some numbers:
Current Size: 2332950 MB
Freespace at end of file: 300 MB
Total freespace: 8957 MB
Blocks Scanned: 10850564
It took 1 hour 44 minutes

The truncation was almost instant.

There appears to be this Using Log Monitor.

I use external tools to examine logs like cconsole.log though.

Was so happy to discover d ConvertShadowDatabases^MIRROR

First my experience is on IRIS.DATs that were 2Tb is size and experience will vary widely since where the free space is is what matters.

There are two different compacts:
Compact globals in a database
Compact free space in a database

If all you want to do is compact free space things are easier.
Do it in small steps with ^DATABASE

Current Size: 2307950 MB
Total freespace: 8564 MB
Freespace at end of file: 18 MB

Target freespace at end of file, in MB (18-8564):200

One great feature is you can cancel if you need to.
Press 'Q' to return, 'P' to pause, 'C' to cancel:

Truncation can be done in the same way in steps.

If you have one I suggest that you do this on your DR instance, move to DR and then do it on what was production.

If you are using 8k blocks for IRIS you should start thinking about the 32Tb limit for 8k databases.

You need to run an integrity check after you are done.

If you wanted to run compact globals that is much more complex.

If the underlying storage does deduplication you should make sure you have extra space at that layer.

AIX 7.3 TL1 defaults to OpenSSL 3.x
$oslevel -s ; openssl version ; uptime
7300-01-02-2320
OpenSSL 3.0.8 7 Feb 2023 (Library: OpenSSL 3.0.8 7 Feb 2023)
  08:58AM   up 72 days,  11:32,  16 users,  load average: 7.04, 8.57, 9.52

I ran your code against a production snapshot and got:
elapsed: 7365.54051
w count
57434071

and

elapsed: 10925.91166
w count
43841315

As you pointed this is a problem in approach.

This is on enterprise hardware so that is not the issue.

I did change your code to use a second subscript ^XXX("YYY",sub)

as an example of a better approach
w $Order(^XXX("YYY",""),-1)
57435810

You can compact the globals inside the IRIS.DAT files.

You can purge journal files automatically.

These are all short term measures unless something is wrong and you can fix the root cause.

From Replacements for ObjectScript $ZUTIL Functions

I think this is only true for locksiz=0 which is the default.

If you set it to a value that is what it is.

Locks are part of gmheap but you could allocate them in advance locksiz.
Can you run irisstat?

Did you try IRIShung?

locksiz is in bytes, uses a subset of gmheap memory and is dynamic. Here it the older Cache version.

gmheap is in megabytes and is static. The default in IRIS is 0.75% of total RAM. Here is the older Cache version.

You can monitor memory usage in the System Management Portal.