(DOCS-15807): Add details for oplog hole (#4110)

* (DOCS-15807): Add details for oplog hole

* fix include file name

* minimalism

* change w:1 formatting

Author: jeff-allen-mongo

source/core/replica-set-rollbacks.txt

@@ -144,6 +144,8 @@ If the operation to roll back is a collection drop or a document
 deletion, the rollback of the collection drop or document deletion
 is not written to the rollback data directory.
 
+.. include:: /includes/w-1-rollback-warning.rst
+
 Read Rollback Data
 ~~~~~~~~~~~~~~~~~~
 

source/includes/w-1-rollback-warning.rst

@@ -0,0 +1,6 @@
+.. warning::
+   
+   In MongoDB 4.4 and later, if write operations use
+   :writeconcern:`{ w: 1 } <\<number\>>` write concern, the rollback
+   directory may exclude writes submitted after an :term:`oplog hole`
+   if the primary restarts before the write operation completes.

source/reference/glossary.txt

@@ -724,6 +724,13 @@ Glossary
       basic mechanism enabling :term:`replication` in MongoDB.
       See :doc:`/core/replica-set-oplog`.
 
+   oplog hole
+      A temporary gap in the oplog due to oplog writes not occurring in
+      sequence. Replica set :ref:`primaries <replica-set-primary>` apply
+      oplog entries in parallel as a batch operation. As a result,
+      temporary gaps in the oplog can occur from entries that are not
+      yet written from a batch.
+
    oplog window
       .. include:: /includes/replication/fact-oplog-window-definition.rst
 

source/reference/write-concern.txt

@@ -128,6 +128,8 @@ available:
          if the primary steps down before the write operations have
          replicated to any of the secondaries.
 
+         .. include:: /includes/w-1-rollback-warning.rst
+
        ``w: 0``
          Requests no acknowledgment of the write operation. However, ``w:
          0`` may return information about socket exceptions and
@@ -498,4 +500,3 @@ Write Concern Contrasted with Commit Quorum
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 .. include:: /includes/indexes/commit-quorum-vs-write-concern.rst
-