Gpcopy migration/using docs (#5074)

* docs -draft update for migrating with gpcopy

* docs - migrating w/ gpcopy - updated ditamap

* add 'pivotal' condition

* some edits, additions, reorg

* removing ssh as a requirement (per comment on related PR)

* Clarifying that same-cluster copies aren't supported

* 4.3.16 -> 4.3.26

* replace --truncate with --truncate-source-after

* add note to start clusters in restricted mode

* add note about md5 validation when migrating between major version

* add pg_dump, pg_dumpall, psql dependencies in prerequisites section

* add info about actual free space needed for migration

* updating discussion of free space calculation

* updating to use new gpcopy option names

* more updates to clarify migration proc

* removing contentious statement about indexing (not present in main docs); adding resource groups to list of objects copied

* removing note about md5xor not working for version migration

* add note regarding validation with --append

* add note to install client package to get gpcopy dependencies

* removed --no-compression info as that's the default for same-host copies; relocated basic migration instructions

* replacing error section with reviewed info from ref page

* updating migration topics to use procedure format

* adding some post-migration steps for gpcopy

* address more feedback from brian; reorganize migration steps a bit; add general post-migration instructions from the relnotes

gpdb-doc/dita/admin_guide/admin_guide.ditamap

@@ -15,14 +15,18 @@
             <topicref href="intro/about_statistics.xml"/>
         </topicref>
         <topicref href="managing/partII.xml" id="partII">
-            <topicref href="managing/versioning.xml" navtitle="About the Greenplum Database Release Version Number"/>
+            <topicref href="managing/versioning.xml"
+                navtitle="About the Greenplum Database Release Version Number"/>
             <topicref href="managing/startstop.xml" navtitle="Starting and Stopping Greenplum"/>
             <topicref href="access_db/access_db.ditamap" format="ditamap"/>
             <topicref href="configure.ditamap" format="ditamap"/>
             <topicref href="highavail/highavail.ditamap" format="ditamap"/>
             <topicref href="managing/backup.ditamap" format="ditamap"/>
             <topicref href="expand/expand.ditamap" format="ditamap"/>
-            <topicref href="managing/gptransfer.xml"/>
+            <topicref href="managing/migrating-data.xml">
+                <topicref href="managing/gpcopy-migrate.xml" otherprops="pivotal"/>
+                <topicref href="managing/gptransfer.xml"/>
+            </topicref>
             <topicref href="managing/monitor.xml" navtitle="Monitoring a Greenplum System"/>
             <topicref href="managing/maintain.xml" navtitle="Routine System Maintenance Tasks"/>
             <topicref href="monitoring/monitoring.dita"/>
@@ -34,8 +38,8 @@
                 <topicref href="kerberos.xml" navtitle="Setting up Kerberos Authentication"
                     id="kerberos"/>
                 <topicref href="kerberos-lin-client.xml"/>
-                <topicref href="kerberos-win-client.xml" navtitle="Configuring Kerberos For Windows Clients"
-                    id="kerberos-win"/>
+                <topicref href="kerberos-win-client.xml"
+                    navtitle="Configuring Kerberos For Windows Clients" id="kerberos-win"/>
             </topicref>
             <topicref href="roles_privs.xml" navtitle="Managing Roles and Privileges"
                 id="roles_privs"/>
@@ -44,7 +48,8 @@
         <topicref href="distribution.xml"/>
         <topicref href="dml.xml" navtitle="Managing Data" id="dml"/>
         <topicref href="query/query.ditamap" navtitle="Querying Data" format="ditamap"/>
-        <topicref href="external/external-tables.ditamap" navtitle="Working with External Data" format="ditamap"/>
+        <topicref href="external/external-tables.ditamap" navtitle="Working with External Data"
+            format="ditamap"/>
         <topicref href="load/load.ditamap" navtitle="Loading and Unloading Data" format="ditamap"/>
         <topicref href="partV.xml">
             <topicref href="perf_intro.xml" navtitle="Defining Database Performance" id="perf_intro"/>
@@ -53,10 +58,11 @@
             <topicref href="wlmgmt_intro.xml" navtitle="Workload Management Resource Overview"
                 id="wlmgmt_intro"/>
             <topicref href="wlmgmt.xml" navtitle="Managing Workload and Resources" id="wlmgmt">
-                <topicref href="workload_mgmt.xml" navtitle="Managing Workloads with Resource Queues"
-                id="workload_mgmt"/>
-                <topicref href="workload_mgmt_resgroups.xml" navtitle="Managing Workloads with Resource Groups"
-                id="workload_mgmt_resgroups"/>
+                <topicref href="workload_mgmt.xml"
+                    navtitle="Managing Workloads with Resource Queues" id="workload_mgmt"/>
+                <topicref href="workload_mgmt_resgroups.xml"
+                    navtitle="Managing Workloads with Resource Groups" id="workload_mgmt_resgroups"
+                />
             </topicref>
             <topicref href="perf_troubleshoot.xml" navtitle="Investigating a Performance Problem"
                 id="perf_troubleshoot"/>

gpdb-doc/dita/admin_guide/managing/migrating-data.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
+<topic id="topic_isj_khw_sbs">
+  <title>Migrating Data</title>
+  <body>
+    <p>Greenplum Database provides utilities that you can use to migrate data between Greenplum
+      Database systems.</p>
+    <p otherprops="pivotal">The <codeph>gpcopy</codeph> utility can require less disk space to
+      migrate between Greenplum Database systems that co-exist on the same hosts. </p>
+    <p>The <codeph>gpransfer</codeph> utility can migrate data between system with a different
+      number of segment instances.</p>
+  </body>
+</topic>