chore: explain read only mode in more detail

apps/docs/pages/guides/platform/database-size.mdx

@@ -89,11 +89,28 @@ In read-only mode, clients will encounter errors such as `cannot execute INSERT
 
 You can manually override read-only mode to reduce disk size. To do this, run the following in the [SQL Editor](https://supabase.com/dashboard/project/_/sql):
 
+To change the [transaction access mode](https://www.postgresql.org/docs/current/sql-set-transaction.html) for the current transaction:
+
 ```sql
 SET TRANSACTION READ WRITE;
 ```
 
 This allows you to delete data from within the session. After deleting data, you should run a vacuum to reclaim as much space as possible.
+You can also change the default transaction access mode for all subsequent transactions of a session:
+
+```sql
+SET SESSION CHARACTERISTICS AS TRANSACTION READ WRITE;
+```
+Ater deleting data, you should run a vacuum to reclaim as much space as possible.
+
+```sql
+VACUUM;
+```
+After completing this in a session, then you can run the following to disable [read-only](https://www.postgresql.org/docs/current/runtime-config-client.html#GUC-DEFAULT-TRANSACTION-READ-ONLY) mode:
+
+```SQL
+SET default_transaction_read_only = 'off';
+```
 
 export const Page = ({ children }) => <Layout meta={meta} children={children} />