Creating and managing Secondary user stores via UI with WSO2 API Manager for two Tenants

Get a WSO2 API Manager pack (latest API Manager 1.8.0)
You can download it from here.

Extract the archive file to a preferred location as a folder for API Manager.
I will be referring to it as <APIM_HOME> in this post.

Using MySQL as the database
So that we should copy MySQL JDBC driver to <APIM_HOME>/repository/components/lib directory

Need to point WSO2AM_DB to a MySQL DB
For that you need to change the DB details accordingly in master-datasources.xml which is inside
<APIM_HOME>/repository/conf/datasources

ex :
       <datasource>
            <name>WSO2AM_DB</name>
            <description>The datasource used for API Manager database</description>
            <jndiConfig>
                <name>jdbc/WSO2AM_DB</name>
            </jndiConfig>
            <definition type="RDBMS">
                <configuration>
                    <url>jdbc:h2:repository/database  
                     /WSO2AM_DB;DB_CLOSE_ON_EXIT=FALSE</url>
                    <username>wso2carbon</username>
                    <password>wso2carbon</password>
                    <defaultAutoCommit>false</defaultAutoCommit>
                    <driverClassName>org.h2.Driver</driverClassName>
                    <maxActive>50</maxActive>
                    <maxWait>60000</maxWait>
                    <testOnBorrow>true</testOnBorrow>
                    <validationQuery>SELECT 1</validationQuery>
                    <validationInterval>30000</validationInterval>
                </configuration>
            </definition>
        </datasource-->

This is the normal block you get in the API Manager pack. But to point to the MySQL DB the bellow lines need to be changed.
               
                    <url>jdbc:mysql://DBlocationIP:Port/DBname?autoReconnect=true</url>
                    <username>username</username>
                    <password>password</password>
                    <driverClassName>com.mysql.jdbc.Driver</driverClassName>
            
Create a WSO2AM_DB database
Run the mysql.sql (<APIM_HOME>/dbscripts/apimgt) script which is relevant to this DB to create the relevant table

Similar way create 2 DBs for User stores (ex: US1_DB, US2_DB) and run the sql DB scripts (<APIM_HOME>/dbscripts) relevant to them

Start API Manager using the terminal
sh <APIM_HOME>/bin/wso2server.sh

Or you can go inside the <APIM_HOME>/bin and execute the command.
 sh wso2server.sh 

Or if you did not run the DB scripts you can execute the bellow command. But it is always good to run the relevant DB script parallel to the created DB.
wso2server.sh -Dsetup

Log in to the Management Console using the admin user and click Add New Tenant under Configure menu.
Create the Tenants you need, providing relevant details.

Log in to the Management Console from Tenant 1
Navigate to Configure > User Store Management >  Click Add Secondary User Store
Create a user store manager providing relevant details

  ex: creating a JDBC User Store Manager 
  Domain Name : kala1.com
  Driver Name : com.mysql.jdbc.Driver
  Connection URL : jdbc:mysql://DBlocationIP:Port/US1_DB?autoReconnect=true
  Connection Name : MySQLusername
  Connection Password : MySQLpassword

Follow the same steps for Tenant 2 pointing the created US2_DB

Then followed the steps in [1]

*To create the IDN_OAUTH2_ACCESS_TOKEN_A and IDN_OAUTH2_ACCESS_TOKEN_B tables added blocks same as CREATE TABLE IDN_OAUTH2_ACCESS_TOKEN in to mysql.sql file inside <APIM_HOME>/dbscripts/apimgt

Restart the server
Log in from the created Tenants to the API Publisher and Store
Create/Publish APIs
Subscribe and generate access tokens

Created tokens should store separately in IDN_OAUTH2_ACCESS_TOKEN_A and IDN_OAUTH2_ACCESS_TOKEN_B tables

[1] - https://docs.wso2.com/display/AM180/Saving+Access+Tokens+in+Separate+Tables