Monday, 18 October 2021 18:45

Reuse Secondary Hardware for Non-Productive SAP HANA Systems with SAP HANA System Replication

Written by Rohit Kumar Sharma
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Source https://blogs.sap.com/2021/10/19/reuse-secondary-hardware-for-non-productive-sap-hana-systems-with-sap-hana-system-replication/
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In this Article, I am going to explain how we can use Secondary SAP HANA hardware for SAP HANA Non-Productive systems to reduce TCO IT infrastructure.

Let’s take an example of SAP HANA productive landscape along with multi-target SAP HANA HA and DR replication setup with 3 nodes.

Here DC1 and DC2 are having High availability setup with replication mode “SYNC” and DC1 and DC3 are having Disaster Recovery setup with replication mode “ASYNC”.

In this article ,we’ll see how hardware in DC3 can be reused for SAP HANA non-productive systems (in below example ) e.g. if we use hardware in DC3 to operate Non-Productive system then there will no need of separate hardware requirement for Non-Productive system and will be good saving for customer.

HANA 3-tier Replication Setup

When planning to run other systems (SAP HANA Non-Productive or Sandbox Systems) on the secondary system, you need to consider following points:

  • The available hardware resources
  • The table preload option (preload_column_tables)
  • The memory (global_allocation_limit) needed by the secondary system.
  • To save memory resources, switch off the preload of tables on the secondary system using global.ini/ [system_replication]-> preload_column_tables=false.
  • HANA System Replication requires memory on the secondary instance, even if pre-load is off.

Sizing Guideline to determine Memory needed for the SAP HANA Secondary System with Pre-load ( ON or OFF) options:

The table below describes requirements for each combination of table preload and operation mode:

Operation mode Load optionMemory needed for the secondary system (global_allocation_limit)
delta_datashippingPre-load onSet the global_allocation_limit to the same value as the memory available on the primary system.
Pre-load offminimum 64 GB   or
(row store size + 20 GB (if this sum is higher)  –> Please refer below section to determine row store size.
LogreplayPre-load onSet GAL to the same value as on the primary
Pre-load offsize of loaded column tables (in-memory) + row store size +  50 GB –>Please refer below section to determine row store size & loaded column tables (in-memory)
Logreplay_readaccess (HANA 2.0)Pre-load onSet the global_allocation_limit to the same value as the memory available on the primary system.
Pre-load offSet the global_allocation_limit to the same value as the memory available on the primary system.

Determine row store size : Kindly use following SQL statement to measure row store size .

select host, round (sum(page_size*USED_BLOCK_COUNT)/1024/1024/1024,2) as
“RowStore Size GB” from m_data_volume_page_statistics where page_sizeclass
= ’16k-RowStore’ group by host;

Determine loaded column tables (in-memory)  : Kindly use following SQL statement to measure loaded column tables (in-memory).

select host, round(sum(memory_size_in_total)/1024/1024/1024) size_GB from m_cs_tables group by host;

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