Hana Fast Restart Option Configuration 2024

Published on: October 30, 2024

Hana Fast Restart Option Configuration:

Hana Fast Restart Option Configuration details:

In this blog we will explain the Hana database fast restart option and configuration for minimized the downtime.
SAP HANA fast restart option it is use possible to reuse the MAIN data fragments. Actually SAP HANA services restarted then load the data from persistent storage. But this is option SAP HANA service restart without the need to re-load the MAIN data from the persistent storage. That why in this option data quickly reloaded into memory and system downtimes can be minimized.

Fast Restart option stores the MAIN data fragments in tmpfs file systems and Tmpfs file systems can grow and size increase dynamically.

Which operation system and hardware is supported the Hana database then Hana Fast Restart Option also supported.

In this feature can be use scenario for Hana restart, Hana service restart and Hana upgrade/service path.

• Hana Fast reset option is available for Hana High availability systems
• The Hana Fast rest option cab be configure on the different system replication sites independently.
• Please check below document for Hana Fast Restart Option Configuration details.

Preparation

Please find the below steps for SAP HANA Fast restart option configuration.

• In this feature, need to create the mount on the tmpfs file system for each nodes and hana instances.
• Execute the below command and identify the NUMA node.. Example 2 NUMA Nodes has exist. Numa node 1 and numa node2.
• Command:
> # cat /sys/devices/system/node/node*/meminfo | grep MemTotal | awk ‘BEGIN {printf “%10s | %20s\n”, “NUMA NODE”, “MEMORY GB”; while (i++ < 33) printf “-“; printf “\n”} {printf “%10d | %20.3f\n”, $2, $4/1048576}’
• Output you will get the details for NUMA NODE.
• Create the directory and mount for all tmpfs mounts
• Create the directory:
• Commands:
1. > mkdir -p /hana/tmpfs1/<SID>
2. > mkdir -p /hana/tmpfs2/<SID>

• Mounts the File system.
> mount tmpfs<SID>1 -t tmpfs -o mpol=prefer:1 /hana/tmpfs1/<SID>
> mount tmpfs<SID>2 -t tmpfs -o mpol=prefer:2 /hana/tmpfs2/<SID>
• Allow access to the directories:
Commands:
> chown -R <SID>adm:sapsys /hana/tmpfs*/<SID>
> chmod 777 -R /hana/tmpfs*/<SID>
• If you want the limit the size of these mounts and execute the below command for set the size.
• Command:
mount tmpfs<SID>0 -t tmpfs -o mpol=prefer:0,size=250G /hana/tmpfs*/<SID>
• Make sure the after operation system restart/reboot , this File system mounts point available is required.
• Maintain the below entries in the file system table.
• Path for File system table: /etc/fstab
• Command:
>tmpfs<sid>0 /hana/tmpfs0/<sid> tmpfs rw,relatime,mpol=prefer:0,uid=<SID>adm_uid,gid=sapsys_gid 0 0
>tmpfs<sid>1 /hana/tmpfs1/<sid> tmpfs rw,relatime,mpol=prefer:1,uid=<SID>adm_uid,gid=sapsys_gid 0 0

Configuration:

Already Base path parameter is maintained for hana data and hana log storage volume in persistence.
Similarly need to maintained the MAIN data fragments storage location configure the parameter in the global.ini file.

Please check the below steps for maintained the parameter.

• Go to Hana Studio
• Navigate to Configure tab
• Click the Global.ini file and expand the path then select the BASEPATH
• Select the below parameter
• Parameter:
basepath_persistent_memory_volumes
• Maintained the File system mount details in parameter.
• Example:
/hana/tmpfs0/<SID>;/hana/tmpfs1/<SID>

We need to maintained the overall tmpfs memory usage for all NUMA nodes for a given HANA instance and maintained the limit on the size of each mount point.

Please check the below steps for maintained the parameter:

• Go to Hana studio
• Navigate to Configure tab
• Click the Global.ini file and expand the path then select the memorymanager
• Select the below parameter
• Parameter:
• persistent_memory_global_allocation_limit
• Maintained the File system mount details in parameter. usually 95% of total filesystem space of configured NVM basepaths
• Example:
• Enter the volume in MB.
use the parameter persistent_memory_global_allocation_limit to restrict the used tmpfs size for File system.

Unloading Tables from Memory:

The standard option is available for unload statement and also unload the tables in Hana database service . This option is use for low memory.
This option used to control the unload behavior of the load the tables.

Please check the below steps for maintained the parameter:

• Go to Hana studio
• Navigate to Configure tab
• Click the indexserver.ini and expand the path then select the persistent_memory
• Select the below parameter
• Parameter:
table_unload_action
• The default value of the parameter for tmpfs is DELETE
• If it is maintained the DELETE then MAIN data fragments are cleared from tmpfs.
• If it is required, Then Please maintain the parameter volume is RETAIN.

Other information:

The Hana monitoring views can be used by the persistent memory and Fast reset option feature also used. The PERSISTENT MEMORY column below parameter is show true then real persistent or Tmpfs is enabled.

• M_CS_TABLES
• M_CS_COLUMNS
• M_CS_ALL_COLUMNS

How to load the data into memory for HANA Fast restart option?

Normally After Hana restart data table loaded from persistent storage to memory, But Hana Fast restart option data loaded from tmsfs to memory. That why Hana services Restarted speedily.

Conclusion:
We have successfully explained the Hana Fast Restart Option Configuration details. we can use the Hana Fast Restart option for High HA System Replication systems.

FAQ for Hana Fast Restart Option Configuration: