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Introduction

In the upcoming weeks, we will be posting new videos to the SAP HANA Academy to show new features and functionality introduced with SAP HANA 2.0 Support Package Stack (SPS) 02.

The topic of this blog is high availability.

For the previous versions of this blog, see

For the full SAP HANA 2.0 SPS 02 blog list, see

 

Tutorial Video

URL: https://www.youtube.com/watch?v=s3MYBHo8664

What’s New?

Row Store Table Types Read Enabled

SAP HANA 2.0 introduced the Active/Active (read enabled) system replication operation mode, which allows read-only access to the secondary site. Initially, only column store tables were supported. As of SPS 02, all row store table types are now supported as well. The only table type not yet supported are column store no-logging tables.

For more information about Active/Active (read enabled) system replication, see

 

Dynamic Tiering

As of SPS 02, using Active/Active (read enabled) in combination with Dynamic Tiering is now supported. This does not yet provide read access to data stored in the dynamic tiering service but it does mean that the presence of DT no longer prohibits the configuration of the read enabled operation mode.

There have been a number of changes in for Dynamic Tiering support with system replication, for the  full list see the DT SP 02 release note and the DT support SAP note

 

Copying and Moving Tenant Databases in a System Replication Landscape (Changed)

It is now possible to copy or move a tenant database to or from a primary system in a running system replication configuration.

The process to copy (or move) a tenant database has not changed.

There are a number of prerequisite steps to enable the secure communication.

For the details, see

Some of the steps can be performed using HANA cockpit but not all as a SQL interface is required to create the tenant as copy and to finalise the operation.

 

-- Step 0  
-- Prepare tenant copy
CREATE CREDENTIAL 
  FOR COMPONENT 'DATABASE_REPLICATION' 
  PURPOSE 'mo-1caae8fcb.mo.sap.corp:30201' 
  TYPE 'PASSWORD' 
  USING 'user="DATABASE_ADMIN";password="*****"'

-- Step 1 
-- Create a tenant database as copy
CREATE DATABASE training 
  AS REPLICA OF CRM 
  AT 'mo-1caae8fcb.mo.sap.corp:30201';

-- Step 2
-- Monitor progress of data replication
SELECT REPLICATION_STATUS 
  FROM SYS_DATABASES.M_DATABASE_REPLICAS;

-- Step 3 
-- Finalize replication when status is ACTIVE
ALTER DATABASE training 
  FINALIZE REPLICA; -- to copy
-- to move
-- ALTER DATABASE training FINALIZE REPLICA DROP SOURCE DATABASE;

 

The tenant copy replication status (step 2), is also displayed in cockpit.

 

srReadAccessInitialized (New)

To enable the automation of additional tasks during the host auto-failover and system replication takeover process, SAP HANA system replication includes a Python-based API for the nameserver process. For example, to first stop the development system on the secondary site just before takeover. We refer to these as “hooks” or, more elegantly, HA/DR providers.

SAP HANA 2.0 SPS 01 added the srServiceStateChanged() provider. In SPS 02, we have added the srReadAccessInitialized() provider, which shows on the primary system when the SQL ports are open on the secondary system.

There is a sample HADR provider Python script file included which includes the code.

[ /usr/sap/<SID>/HDB##/exe/python_support/hdb_ha_dr/HADRDummy.py ]

    def srServiceStateChanged(self, parameters, **kwargs):
        self.tracer.debug
         ("enter srServiceStateChanged hook; %s" % locals())

        # Access to parameters dictionary
        hostname = parameters['hostname']
        service = parameters['service_name']
        port = parameters['service_port']
        status = parameters['service_status']
        timestamp = parameters['timestamp']

        self.tracer.info("leave srServiceStateChanged hook")
        return 0

 

Alert ID 104: System Replication Increased Log Shipping Backlog (New)

A new alert has been added to the family, adding up the total to 115.

Alert 104 Log shipping backlog for system replication secondary is raised when the backlog is increased, which may cause issues (data loss) on the secondary system in case a takeover is performed.

For the details, see

 

Secondary Read Access (New)

The header for System Replication Overview in the SAP HANA cockpit now informs us if secondary read access is enabled or pending – in case the operation mode is configured for LOGREPLAY_READACCESS – and about the network security settings.

 

Network Security Settings (New)

In cockpit, you can now also view your replication-related network security settings on the System Replication Overview page.

Note that the default settings with listeninterface = .global, SSL= off, and no allowed sender specified is not secure at all, so make sure to review

 

Monitor Network (New)

Finally, a link has been added to the cockpit Overview page for direct access to the Monitor Network page.

On this page, you can perform a network speed check using the Measure Network Speed link with a ping or by sending 1, 10, 100, or 1000 MB over the network.

Documentation (New)

Two new sections have been added to the SAP HANA Administration guide on the topic of high availability for XS Advanced model

 

Playlist

On the SAP HANA Academy, there is a full playlist covering all aspects of system replication:

 

Documentation

For more information, see:

SAP Help Portal

 

SAP Notes

 

White Paper

 

SAP HANA Blogs

 

Thank you for watching

The SAP HANA Academy provides technical enablement, implementation and adoption support for customers and partners with 1000’s of free tutorial videos.

For the full library, see SAP HANA Academy Library – by the SAP HANA Academy.

For the full list of blogs, see Blog Posts – by the SAP HANA Academy.

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