Merge pull request #35714 from PiJoCoder/update-p2p-repl-pijocoder-asavioli-110325

create an article on peer-to-peer replication update

Author: denrea

docs/database-engine/install-windows/upgrade-peer-to-peer-replicated-databases.md

@@ -0,0 +1,99 @@
+---
+title: Upgrade or Patch Peer-to-Peer Replicated Databases
+description: SQL Server supports upgrading Peer-to-Peer replicated databases from previous versions of SQL Server without stopping activity on other peers.
+author: asavioliMSFT
+ms.author: akbarf
+ms.reviewer: jopilov, mathoma
+ms.date: 12/12/2025
+ms.service: sql
+ms.subservice: install
+ms.topic: upgrade-and-migration-article
+helpviewer_keywords:
+  - "peer-to-peer replication database upgrades [SQL Server replication]"
+  - "replication [SQL Server], upgrading upgrade-peer-to-peer-replication.md"
+  - "transactional replication, upgrading databases"
+  - "p2p replication [SQL Server], upgrading databases"
+  - "upgrading replicated databases"
+monikerRange: ">=sql-server-2016"
+---
+
+# Upgrade or patch peer-to-peer replicated databases
+
+[!INCLUDE [SQL Server -Windows Only](../../includes/applies-to-version/sql-windows-only.md)]
+
+This article provides guidance on how to upgrade or patch SQL Server instances that participate in [peer-to-peer (P2P) replication](../../relational-databases/replication/transactional/peer-to-peer-transactional-replication.md), both outside of an Always On availability group and for databases that are within an Always On availability group.
+
+If your replication topology includes other types of replication, such as snapshot, merge or transactional replication, see [Upgrade or patch replicated databases](upgrade-replicated-databases.md) for more information.
+
+## Upgrade P2P databases outside of an availability group
+
+The steps in this section provide guidance on how to upgrade or patch SQL Server instances that are participating in peer-to-peer (P2P) replication outside of an Always On availability group.
+
+The following table describes the roles and names of the servers that participate in the replication topology used in the example:
+
+| Name | Role |
+| --- | --- |
+| **Peer1** | The SQL Server instance that hosts the replication databases for the first peer in the peer-to-peer topology. |
+| **Peer2** | The SQL Server instance that hosts the replication databases for the second peer in the peer-to-peer topology. |
+| **Dist1** | The remote distributor for Peer1. |
+| **Dist2** | The remote distributor for Peer2. |
+
+When patching or upgrading peer-to-peer replicated databases outside of an availability group, follow these steps:
+1. Stop incoming traffic to **Peer2** by stopping all applications and distribution agents from any other peers that replicate to this instance. For example, stop the distribution agent on **Peer1**.
+1. Confirm there are no pending replicated transactions coming to **Peer2** by checking the log reader agents and distribution agents associated with this replication topology.
+1. If the distributor is remote, first upgrade the remote distributor **Dist2**. If the distributor is the local **Peer2** instance, skip to the next step.
+1. Upgrade the instance **Peer2**.
+1. Start the distribution agent from **Peer1** (or any remaining peers replicating to this peer).
+1. Stop incoming traffic to **Peer1** by stopping all applications and distribution agents from any other peers that replicate to this instance. For example, stop the distribution agent on **Peer2**.
+1. Confirm there are no pending replicated transactions coming to **Peer1** by checking the log reader agents and distribution agents associated with this replication topology.
+1. If the distributor is remote, first upgrade the remote distributor **Dist1**. If the distributor is the local **Peer1** instance, skip to the next step.
+1. Upgrade the instance **Peer1**.
+1. Start the distribution agent from **Peer2** (or any remaining peers replicating to this peer).
+1. If there are any other peers in the topology, repeat these same steps for each peer.
+
+## Upgrade P2P databases in an availability group
+
+The steps in this section provide guidance on how to upgrade or patch SQL Server instances that are participating in peer-to-peer (P2P) replication within an Always On availability group.
+
+The following table describes the roles and names of the servers that participate in the replication topology used in the example:
+
+| Name | Role |
+| --- | --- |
+| **Peer1N1** | The SQL Server instance that hosts the primary replica, and is **Peer1** in the peer-to-peer topology. |
+| **Peer1N2** | The SQL Server instance that hosts the secondary replica associated with **Peer1** in the peer-to-peer topology. |
+| **Dist1** | The remote distributor for **Peer1**. |
+| **Peer2N3** | The SQL Server instance that hosts the primary replica, and is **Peer2** in the peer-to-peer topology. |
+| **Peer2N4** | The SQL Server instance that hosts the secondary replica associated with **Peer2** in the peer-to-peer topology. |
+| **Dist2** | The remote distributor for **Peer2**. |
+
+> [!NOTE]  
+> Using a local distributor for a P2P database that is part of an availability group isn't a recommended configuration, as it's a single point of failure.
+
+When patching or upgrading peer-to-peer replicated databases within an availability group, follow these steps:
+1. Stop incoming traffic to **Peer2** by stopping all applications and distribution agents from any other peers that replicate to this instance. For example, stop the distribution agent on **Peer1**.
+1. Confirm there are no pending replicated transactions coming to **Peer2** by checking the log reader agents and distribution agents associated with this replication topology.
+1. Upgrade the remote distributor for **Peer2**, **Dist2**, by following the sequence in [Upgrade availability group replicas](../availability-groups/windows/upgrading-always-on-availability-group-replica-instances.md). If your distributor is local, skip to the next step.
+1. Upgrade the secondary replica **Peer2N4**.
+1. Perform a failover of the availability group from the current primary replica **Peer2N3** to the upgraded secondary **Peer2N4**.
+1. Upgrade the former primary replica **Peer2N3**.
+1. Perform a failover of the availability group from the current primary **Peer2N4** to the previous primary replica **Peer2N3**.
+1. Start the distribution agent from **Peer1** (or any remaining peers replicating to this peer).
+1. Stop incoming traffic to **Peer1** by stopping all applications and distribution agents from any other peers that replicate to this instance. For example, stop the distribution agent on **Peer2**.
+1. Confirm there are no pending replicated transactions coming to **Peer1** by checking the log reader agents and distribution agents associated with this replication topology.
+1. Upgrade the remote distributor for **Peer1**, **Dist1**, by following the sequence in [Upgrade availability group replicas](../availability-groups/windows/upgrading-always-on-availability-group-replica-instances.md). If your distributor is local, skip to the next step.
+1. Upgrade the secondary replica **Peer1N2**.
+1. Perform a failover of the availability group from the current primary replica **Peer1N1** to the upgraded secondary **Peer1N2**.
+1. Upgrade the former primary replica **Peer1N1**.
+1. Perform a failover of the availability group from the current primary **Peer1N2** to the previous primary replica **Peer1N1**.
+1. Start the distribution agent from **Peer2** (or any remaining peers replicating to this peer).
+1. If there are any other peers in the topology, repeat these same steps for each peer.
+
+## Related content
+
+- [SQL Server Replication](../../relational-databases/replication/sql-server-replication.md)
+- [Upgrade or patch replicated databases](upgrade-replicated-databases.md)
+- [Replication Administration FAQ](../../relational-databases/replication/administration/frequently-asked-questions-for-replication-administrators.yml)
+- [Replication backward compatibility](../../relational-databases/replication/replication-backward-compatibility.md)
+- [Supported version and edition upgrades (SQL Server 2022)](supported-version-and-edition-upgrades-2022.md)
+- [Upgrade SQL Server](upgrade-sql-server.md)
+- [Upgrade availability group replicas](../availability-groups/windows/upgrading-always-on-availability-group-replica-instances.md)

docs/database-engine/install-windows/upgrade-replicated-databases.md

@@ -21,6 +21,8 @@ monikerRange: ">=sql-server-2016"
 
 [!INCLUDE [ssNoversion](../../includes/ssnoversion-md.md)] supports upgrading replicated databases from previous versions of [!INCLUDE [ssNoVersion](../../includes/ssnoversion-md.md)]; it isn't required to stop activity at other nodes while a node is being upgraded.
 
+For peer-to-peer replication, see [Upgrade or patch Peer-to-peer replicated databases](upgrade-peer-to-peer-replicated-databases.md).
+
 ## Prerequisites
 
 Ensure that you adhere to the rules regarding which versions are supported in a topology:

docs/toc.yml

@@ -4457,8 +4457,10 @@ items:
       href: database-engine/install-windows/upgrade-master-data-services.md
     - name: Power Pivot for SharePoint
       href: database-engine/install-windows/upgrade-power-pivot-for-sharepoint.md
-    - name: Replicated Databases
+    - name: Replicated databases
       href: database-engine/install-windows/upgrade-replicated-databases.md
+    - name: Peer-to-peer replicated databases
+      href: database-engine/install-windows/upgrade-peer-to-peer-replicated-databases.md
     - name: SQL Server Management Tools
       href: database-engine/install-windows/upgrade-sql-server-management-tools.md
     - name: Installation Wizard (Setup)