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     Latest SAP software versions are including many new functionalities customers were waiting anxiously and some of the most interesting ones are in the SAP Replication Server and SAP ASE areas. SAP Replication Server 15.7.1 SP204-SP300 for instance includes enhancements for heterogeneous replication (non source/target SAP DBMSs) and also enhancement for SAP HANA as replicate, and SAP ASE 16.0 SP2 includes interesting features like Data Store Access Management (called DSAM), Workload Analyzer and HADR for customer applications. This last feature, namely HADR, is the one I am going to focus on in this blog, it is also called SAP ASE Database Always-On and it is implemented using SAP Replication Server underneath.



     Architecture


     The SAP ASE HADR or Always-On option consist on 2 SAP ASE servers one of them acting as primary or active database server and the other one as standby database server, all transactions take place in the primary server and are copied/applied to the standby server so that is can be used as HA or DS server in case of problems with the primary database server.

     This is the big picture for HADR architecture:

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     There are 2 replication paths defined, one for each way, but only one of them is active at a time, that is, replication takes place only from the primary database server to the standby one and application connections to the standby side are automatically redirected to the primary database server transparently from application point of view.



     Components

  • 2 SAP ASE servers.
  • 2 SAP Replication Servers, one in each of the SAP ASE hosts.
  • 2 RMAs. Replication Management Agents are used to access SAP ASE and SRS locally to execute replication server system tasks.
  • 2 Host Agents one in each host. They are responsible for life-cycle management tasks, such as operating-system monitoring, database monitoring, system instance control, and provisioning.
  • Fault Manager that is responsible for failing over in case of problems (installed in a separate host).
  • SAP ASE Cockpit (SCC monitoring) as administration and monitoring tool.


    

     Remarks


  • Automatic failover performed by the Fault Manager.
  • Easy configuration with SAP tools: SAP ASE installer or “setuphadr” utility.
  • Easy monitoring and administration with SAP ASE Cockpit GUI.
  • Synchronous (HA) or asynchronous (DR) data copy in the standby depending on the requirements.


    

     HA or DR configuration

     This new SAP ASE feature allows the SAP ASE servers located both together or separated geographically:

    • When they are together Always-On option offers a High Availability system (HA) with zero data loss, very low down time implemented with synchronous replication and automatic failover
    • When they are separated geographically the Always-On option offers a Disaster Recovery system (DR) with near zero data loss, minimal down time implemented with asynchronous replication and manual failover.


     The recommendation is use an HA solution when the 2 sites are separated around a few tens of kilometers and DR when they are separated hundreds of kilometers.



    SAP ASE Cockpit for HADR monitoring and administration

     SAP ASE Cockpit includes the needed stuff to monitor and administer and SAP ASE 16.0 SP02 HADR system. Following screen shots show the nice appearance easy to use:


     Monitoring:

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.     Administering:


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More details in SAP Sybase documentation:


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