Backport to 7.0: (DOCSP-37680) Remove -Xmn for G1GC in OM7 (#151) (#152)

This is backporting of #151 to 7.0
[DOCSP-37680](https://jira.mongodb.org/browse/DOCSP-37680)


[Build](https://workerpool-boxgs.mongodbstitch.com/pages/job.html?collName=queue&jobId=65faff116fc5f04850485a96)

Author: JuliaMongo

source/includes/extracts-troubleshooting.yaml

@@ -230,21 +230,18 @@ content: |
 
               .. warning:: Do not change other Java options
 
-                 Changing any option values other than ``-Xmx``, 
-                 ``-Xms``, and ``-Xmn`` could have an unexpected impact 
+                 Changing any option values other than ``-Xmx`` and
+                 ``-Xms`` could have an unexpected impact 
                  on the |application|. Do not change other values 
                  without consulting MongoDB Support.
 
            
-           3. Change the ``-Xmx``, ``-Xms``, and ``Xmn`` values:
+           3. Change the ``-Xmx`` and ``-Xms`` values:
    
               - Change the ``-Xmx`` and ``-Xms`` values to a larger
                 value. You should set both parameters to the same value
                 to remove any performance impact from the VM constantly
                 reclaiming memory from the heap.
-
-              - Change the ``-Xmn`` value to a quarter of the value 
-                that you specified for the ``-Xmx`` and ``-Xms`` keys.
               
               Specify the values as ``#k|m|g``: a number followed 
               by:
@@ -256,7 +253,7 @@ content: |
               .. example::
 
                  To set the Java Heap to 12 :abbr:`GB (Gigabytes)`, 
-                 set the values to: ``-Xmx12g -Xms12g -Xmn3g``.
+                 set the values to: ``-Xmx12g -Xms12g``.
 
        - id: windows
          name: Windows Hosts

source/reference/troubleshooting/system.txt

@@ -50,21 +50,21 @@ hosts:
 
    .. warning:: **Do not change other Java options**
 
-      Changing any option values other than ``-Xmx``, 
-      ``-Xms``, and ``-Xmn`` could have an unexpected impact 
+      Changing any option values other than ``-Xmx`` and
+      ``-Xms`` could have an unexpected impact 
       on the |application|. Do not change other values 
       without consulting MongoDB Support.
+      Starting with |onprem| 7.0, |onprem| adopted a Garbage-First
+      Garbage Collector (G1GC) method for the JVM. Don't use ``-Xmn``
+      to set the size of the heap for the young generation.
 
-3. Change the ``-Xmx``, ``-Xms``, and ``Xmn`` values:
+3. Change the ``-Xmx`` and ``-Xms`` values:
 
    - Change the ``-Xmx`` and ``-Xms`` values to a larger
      value. You should set both parameters to the same value
      to remove any performance impact from the VM constantly
      reclaiming memory from the heap.
 
-   - Change the ``-Xmn`` value to a quarter of the value 
-     that you specified for the ``-Xmx`` and ``-Xms`` keys.
-
    Specify the values as ``#k|m|g``: a number followed 
    by:
 
@@ -75,7 +75,7 @@ hosts:
    .. example::
 
       To set the Java Heap to 12 :abbr:`GB (Gigabytes)`, 
-      set the values to: ``-Xmx12g -Xms12g -Xmn3g``.
+      set the values to: ``-Xmx12g -Xms12g``.
 
 4. Restart each host running |a-mms| instance on which you made these
    changes.

source/tutorial/monitoring-large-deployments.txt

@@ -11,7 +11,7 @@ Configure Ops Manager to Monitor Large Deployments
    :class: singlecol
 
 To monitor deployments with more than 2,000 hosts located in
-globally-distributed datacenters, configure your |onprem| instance
+globally-distributed data centers, configure your |onprem| instance
 with these advanced settings.
 
 Allocate more RAM to Ops Manager Hosts
@@ -21,13 +21,24 @@ Allocate more RAM to Ops Manager Hosts
    editor.
 
 2. Find a line where the ``JAVA_MMS_UI_OPTS`` variable defines the
-   ``-Xms``, ``-Xmx``, and ``-Xmn`` parameters.
+   ``-Xms`` and ``-Xmx`` parameters.
 
 3. Update the ``-Xms`` and ``-Xmx`` values from the default of 4352 MB 
    to 8192 MB or more if the hosts have extra free memory.
 
-4. Update the ``-Xmn`` value from the default of 1500 MB to a quarter 
-   of the value that you specified for ``-Xms`` and ``-Xmx``.
+   .. note:: Don't Set Young Generation's Heap Size Explicitly Using ``-Xmn``.
+
+      Starting with |onprem| 7.0, |onprem| adopted a Garbage-First (G1)
+      garbage collector method for the JVM. We recommend that you don't
+      set the young generation's heap size explicitly to any fixed value
+      using ``-Xmn``. Setting a fixed value with ``-Xmn`` interferes with
+      the G1 garbage collector's default behavior. If you set this value,
+      this prevents the G1 garbage collector from expanding and contracting
+      the young generation space as needed, which causes the collector to
+      stop respecting the pause time value for garbage collections.
+      
+      You can set the values for ``Xmx`` and ``Xms`` to be the same, and
+      retain the pause at its default value: ``-XX:MaxGCPauseMillis=200``.
 
 To learn about how to resolve this error in greater detail, see our
 troubleshooting entry on the
@@ -76,4 +87,4 @@ ingestion:
       mms.monitoring.rrd.rawsystem.batch.size=1000
 
 3. Save the properties file.
-4. Restart Ops Manager.
+4. Restart |onprem|.