Added Note 2 in xdcr eccv page

Author: rao-shwe

modules/learn/pages/clusters-and-availability/xdcr-enable-crossclusterversioning.adoc

@@ -12,6 +12,25 @@ Therefore, you must not enable `enableCrossClusterVersioning` casually.
 When you set the bucket property `enableCrossClusterVersioning` (ECCV) to `true`, for each document processed by XDCR, XDCR stores additional metadata for the document in the extended attributes.
 This metadata is also called Hybrid Logical Vector (HLV), which is a set of Hybrid Logical Clock (HLC) information.
 
+[NOTE]
+====
+Cross Cluster Versioning (ECCV) Compatibility with Couchbase Server Versions::
+
+Starting in Couchbase Server 7.6.6, buckets include the `enableCrossClusterVersioning` (ECCV) property, which is set to `false` (disabled) by default.
++
+If you set ECCV to `true` (enabled) on a bucket in an XDCR replication topology,
+then you must set ECCV to `true` on all buckets participating in the XDCR replication topology.
+Otherwise, dependent features may not function.
++
+As the Couchbase Server versions earlier than 7.6.6 do not support the `enableCrossClusterVersioning` bucket property,
+those buckets cannot participate in a replication topology containing ECCV-enabled buckets.
++
+Couchbase Server does not automatically validate ECCV consistency across clusters.
+If you want to enable ECCV, then before creating or modifying XDCR replications, you must manually verify that ECCV is enabled on all participating buckets.
++
+For more information about XDCR compatibility between different versions of Couchbase Server Enterprise edition, see xref:learn:clusters-and-availability/xdcr-overview.adoc#xdcr-compatibility[XDCR Compatibility].
+====
+
 [#hlv-data-maintained-in-xattr]
 == Hybrid Logical Vector (HLV) Data Maintained in the Extended Attributes
 

modules/learn/pages/clusters-and-availability/xdcr-overview.adoc

@@ -349,7 +349,8 @@ Cross Cluster Versioning (ECCV) Compatibility (for ** only)::
 
 Starting in Couchbase Server 7.6.6, buckets include the `enableCrossClusterVersioning` (ECCV) property, which is set to `false` (disabled) by default.
 +
-If you set ECCV to `true` (enabled) on a bucket, then you must set ECCV to `true` on all buckets participating in the XDCR replication topology.
+If you set ECCV to `true` (enabled) on a bucket in an XDCR replication topology,
+then you must set ECCV to `true` on all buckets participating in the XDCR replication topology.
 Otherwise, dependent features may not function.
 +
 As the Couchbase Server versions earlier than 7.6.6 do not support the `enableCrossClusterVersioning` bucket property,