README: update readme for session modes (#2456)

* README: update readme for session modes

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: alkatrivedi

.readme-partials.yml

@@ -28,12 +28,14 @@ body: |-
 
         ## Multiplexed Sessions
 
-        Spanner's Multiplexed Sessions can now be used as an efficient alternative to the default session pool. This feature helps reduce
-        session management overhead and minimize session-related errors. Multiplexed sessions can be enabled for all transaction types via environment variables.
+        Spanner's Multiplexed Sessions is now default enabled session mode in node client. This feature helps reduce
+        session management overhead and minimize session-related errors.
 
-        ### Configuration
+        For a detailed explanation on multiplexed sessions, please refer to the [official documentation](https://cloud.google.com/spanner/docs/sessions#multiplexed_sessions).
 
-        To enable this feature, set the following environment variables to `true`:
+        ## Regular Sessions
+
+        To use regular sessions, disable the multiplexed sessions and set the following environment variables to `false`:
 
         * **For Read-Only Transactions:**
         - `GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS`
@@ -44,4 +46,4 @@ body: |-
         - `GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS`
         - `GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS_FOR_RW`
 
-        For a detailed explanation of this feature, please refer to the [official documentation](https://cloud.google.com/spanner/docs/sessions#multiplexed_sessions).
+        For a detailed explanation on session modes and env configurations, please refer to the [official documentation](https://cloud.google.com/spanner/docs/sessions).

README.md

@@ -104,12 +104,14 @@ Refer to the Observability README to know more about tracing support in the Clou
 
 ## Multiplexed Sessions
 
-Spanner's Multiplexed Sessions can now be used as an efficient alternative to the default session pool. This feature helps reduce
-session management overhead and minimize session-related errors. Multiplexed sessions can be enabled for all transaction types via environment variables.
+Spanner's Multiplexed Sessions is now default enabled session mode in node client. This feature helps reduce
+session management overhead and minimize session-related errors.
 
-### Configuration
+For a detailed explanation on multiplexed sessions, please refer to the [official documentation](https://cloud.google.com/spanner/docs/sessions#multiplexed_sessions).
 
-To enable this feature, set the following environment variables to `true`:
+## Regular Sessions
+
+To use regular sessions, disable the multiplexed sessions and set the following environment variables to `false`:
 
 * **For Read-Only Transactions:**
 - `GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS`
@@ -120,7 +122,7 @@ To enable this feature, set the following environment variables to `true`:
 - `GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS`
 - `GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS_FOR_RW`
 
-For a detailed explanation of this feature, please refer to the [official documentation](https://cloud.google.com/spanner/docs/sessions#multiplexed_sessions).
+For a detailed explanation on session modes and env configurations, please refer to the [official documentation](https://cloud.google.com/spanner/docs/sessions).
 
 
 ## Samples