Add Transaction Configuration section and Access Mode header

Author: gjmwoods

modules/ROOT/pages/actions/index.adoc

@@ -11,6 +11,7 @@ There are several _actions_ that can be performed using the Cypher transaction H
 * xref:actions/query-format.adoc[]
 * xref:actions/result-format.adoc[]
 * xref:actions/routing.adoc[]
+* xref:actions/transaction-configuration.adoc[]
 
 *Using the API:*
 

modules/ROOT/pages/actions/routing.adoc

@@ -19,7 +19,7 @@ The level of support depends on whether link:https://neo4j.com/docs/operations-m
 |Clusters support routing for queries that involve a xref::/actions/begin-and-commit-a-transaction-in-one-request.adoc[single request] (i.e. via the `tx/commit` endpoint).
 This is because the cluster does not currently support transaction identifiers across the cluster.
 
-In this context, all queries are considered `WRITE` queries, even if they contain no cypher with write operations.
-Since the HTTP API did not previously support marking queries as `READ` or `WRITE`, the server assumes all queries are `WRITE` queries to support all cases.
-The effect of this is that all queries are ultimately executed on the leader.
-|===
+By default, all transactions are considered `WRITE` transactions, even if they contain no Cypher with write operations. This can be overridden by setting a value of `READ` in the `access-mode` header of the request (see xref::/actions/transaction-configuration.adoc[Transaction Configuration - Access Mode]).
+
+This default has the effect that all queries are ultimately executed on the leader. To ensure efficient load balancing of `READ` transactions, you must label them as such in the request.
+|===

modules/ROOT/pages/actions/transaction-configuration.adoc

@@ -0,0 +1,15 @@
+[[http-api-actions-transaction-configuration]]
+
+:description: Configuring HTTP Transactions.
+
+
+= Transaction Configuration
+
+For any transaction initiating request (i.e. `/tx` or `tx/commit` ) you can provide configuration options that apply for the duration of the whole transaction.
+
+== Access Mode
+To ensure that efficient load balancing across a cluster, it is important to label transactions that only contain `READ` statements with a `READ` access mode.
+
+This can be done by adding an `access-mode` header to the request with a value of `READ`.
+
+The default value if an `access-mode` configuration has not been provided is `WRITE` (expect for clusters where Server-side routing has been disabled where it is `READ`).