Here I am going to building two APIM instance for high availability. You can try this on two nodes. But here I am trying it in one PC. Therefore I will be changing port offset. I will be using WSO2 AM 4.6.0 for this article.
In Here you will be needing

• MySQL Server.
• MySQL JDBC driver.(mysql-connector-java-x.x.xx-bin.jar)

1. Unzip AM 4.6.0 for two Directories such as node1 and node2
2. Firstly we will setup MYSQL database (Three databases)
My MYSQL username is 'root' and password 'root'

mysql> create database apimgtdb;
mysql> use apimgtdb;
mysql> source <APIM_HOME>/dbscripts/apimgt/mysql.sql;
mysql> grant all on apimgtdb.* TO root@localhost identified by "root";
 
 
mysql> create database userdb;
mysql> use userdb;
mysql> source <APIM_HOME>/dbscripts/mysql.sql;
mysql> grant all on userdb.* TO root@localhost identified by "root";
 
 
mysql> create database regdb;
mysql> use regdb;
mysql> source <APIM_HOME>/dbscripts/mysql.sql;
mysql> grant all on regdb.* TO root@localhost identified by "root";

3. Now we will consider node1 APIM instance

4. Configure the data sources for the three database by adding below for <APIM_HOME>/repository/conf/datasources/master-datasources.xml

(Comment out existing ‘datasource’ for WSO2AM_DB)

<datasource>
        <name>WSO2AM_DB</name>
         <description>The datasource used for the API Manager database</description>
         <jndiConfig>
           <name>jdbc/WSO2AM_DB</name>
         </jndiConfig>
         <definition type="RDBMS">
           <configuration>
             <url>jdbc:mysql://apimgtdb.mysql-wso2.com:3306/apimgtdb?autoReconnect=true&relaxAutoCommit=true</url>
             <username>root</username>
             <password>root</password>
             <driverClassName>com.mysql.jdbc.Driver</driverClassName>
             <maxActive>50</maxActive>
             <maxWait>60000</maxWait>
             <testOnBorrow>true</testOnBorrow>
             <validationQuery>SELECT 1</validationQuery>
             <validationInterval>30000</validationInterval>
           </configuration>
         </definition>
        </datasource>

        <datasource>
         <name>WSO2UM_DB</name>
         <description>The datasource used by user manager</description>
         <jndiConfig>
           <name>jdbc/WSO2UM_DB</name>
         </jndiConfig>
         <definition type="RDBMS">
           <configuration>
             <url>jdbc:mysql://userdb.mysql-wso2.com:3306/userdb?autoReconnect=true&relaxAutoCommit=true</url>
             <username>root</username>
             <password>root</password>
             <driverClassName>com.mysql.jdbc.Driver</driverClassName>
             <maxActive>50</maxActive>
             <maxWait>60000</maxWait>
             <testOnBorrow>true</testOnBorrow>
             <validationQuery>SELECT 1</validationQuery>
             <validationInterval>30000</validationInterval>
           </configuration>
         </definition>
        </datasource>

        <datasource>
         <name>WSO2REG_DB</name>
         <description>The datasource used by user manager</description>
         <jndiConfig>
           <name>jdbc/WSO2REG_DB</name>
         </jndiConfig>
         <definition type="RDBMS">
           <configuration>
             <url>jdbc:mysql://regdb.mysql-wso2.com:3306/regdb?autoReconnect=true&relaxAutoCommit=true</url>
             <username>root</username>
             <password>root</password>
             <driverClassName>com.mysql.jdbc.Driver</driverClassName>
             <maxActive>50</maxActive>
             <maxWait>60000</maxWait>
             <testOnBorrow>true</testOnBorrow>
             <validationQuery>SELECT 1</validationQuery>
             <validationInterval>30000</validationInterval>
           </configuration>
         </definition>
        </datasource>

5. Add '<DataSourceName>jdbc/WSO2AM_DB</DataSourceName>' if not given in the <APIM_HOME>/repository/conf/api-manager.xml

6. Now update <UserStoreManager> element in <APIM _HOME>/repository/conf/user-mgt.xml

<UserStoreManager class="org.wso2.carbon.user.core.jdbc.JDBCUserStoreManager">
           <Property name="TenantManager">org.wso2.carbon.user.core.tenant.JDBCTenantManager</Property>
           <Property name="dataSource">jdbc/WSO2UM_DB</Property>
           <Property name="ReadOnly">false</Property>
           <Property name="MaxUserNameListLength">100</Property>
           <Property name="IsEmailUserName">false</Property>
           <Property name="DomainCalculation">default</Property>
           <Property name="PasswordDigest">SHA-256</Property>
           <Property name="StoreSaltedPassword">true</Property>
           <Property name="ReadGroups">true</Property>
           <Property name="WriteGroups">true</Property>
           <Property name="UserNameUniqueAcrossTenants">false</Property>
           <Property name="PasswordJavaRegEx">^[\S]{5,30}prebuffer_2lt;/Property>
           <Property name="PasswordJavaScriptRegEx">^[\S]{5,30}prebuffer_2lt;/Property>
           <Property name="UsernameJavaRegEx">^[^~!#$;%^*+={}\\|\\\\<>,\'\"]{3,30}prebuffer_2lt;/Property>
           <Property name="UsernameJavaScriptRegEx">^[\S]{3,30}prebuffer_2lt;/Property>
           <Property name="RolenameJavaRegEx">^[^~!#$;%^*+={}\\|\\\\<>,\'\"]{3,30}prebuffer_2lt;/Property>
           <Property name="RolenameJavaScriptRegEx">^[\S]{3,30}prebuffer_2lt;/Property>
           <Property name="UserRolesCacheEnabled">true</Property>
           <Property name="MaxRoleNameListLength">100</Property>
           <Property name="MaxUserNameListLength">100</Property>
           <Property name="SharedGroupEnabled">false</Property>
           <Property name="SCIMEnabled">false</Property>
</UserStoreManager>

6.1 Update DataSourceName as below for point to share DB for permission

<DataSourceName>jdbc/WSO2AM_DB</DataSourceName>

8.  Publisher and Store components access to the registry database, To config it open the <APIM_HOME>/repository/conf/registry.xml and added below lines to it

<dbConfig name="govregistry">
      <dataSource>jdbc/WSO2REG_DB</dataSource>
    </dbConfig>
    <remoteInstance url="https://govregistry.apim-wso2.com">
       <id>gov</id>
       <dbConfig>govregistry</dbConfig>
       <readOnly>false</readOnly>
       <enableCache>true</enableCache>
       <registryRoot>/</registryRoot>
    </remoteInstance>
    <mount path="/_system/governance" overwrite="true">
       <instanceId>gov</instanceId>
       <targetPath>/_system/governance</targetPath>
    </mount>

9. Modify the /etc/hosts (C:\Windows\System32\drivers\etc) entries to map the relevant IP addresses

127.0.0.1   apimgtdb.mysql-wso2.com
127.0.0.1   userdb.mysql-wso2.com
127.0.0.1   regdb.mysql-wso2.com
127.0.0.1   govregistry.apim-wso2.com

10. Node1 is ready for start

setup node2 or node(n)

11. Simply you can copy and past above files files for node 2

12. (*) Change ‘carbon.xml’ offset if you try in same PC rather separate nodes. If you trying in separate node no need to change port offset.

[NOTE]

you offset port change not reflect in thrift server there fore you have changes those manually10397 to 10398 as offset is 1.

    <ThriftClientPort>10398</ThriftClientPort>

    <ThriftServerPort>10398</ThriftServerPort>

  <KeyValidatorClientType>WSClient</KeyValidatorClientType>
        <ThriftClientPort>10397</ThriftClientPort>
        <ThriftClientConnectionTimeOut>10000</ThriftClientConnectionTimeOut>
        <ThriftServerPort>10397</ThriftServerPort>
    <EnableThriftServer>false</EnableThriftServer>

https://10.100.1.112:9443/publisher/

https://10.100.1.112:9443/publisher/ 

Create API and Publish any of the above URL and subscribe to it in store same

Here is same Access Token

Publisher

you need to cluster Gateway, Publisher and Store components for the caches to work properly refer[1]

[1] http://docs.wso2.org/pages/viewpage.action?pageId=29918203

[2] http://docs.wso2.org/display/CLUSTER420/Clustering+API+Manager