How to prevent certain values in limits.conf from being changed by saptune

SUSE Linux Enterprise Server for SAP Applications 12 Service Pack 3

Values that have been manually set in /etc/security/limits.conf are being over-written.

e.g.
@sapsys soft nofile 75000
@sapsys hard nofile 72000
@sdba soft nofile 75000
@sdba hard nofile 72000
@dba soft nofile 80000
@dba hard nofile 80000

The above values are being over-written and reset to:-

@sapsys soft nofile 65536
@sapsys hard nofile 65536
@sdba soft nofile 65536
@sdba hard nofile 65536
@dba soft nofile 65536
@dba hard nofile 65536

The normal workflow for this situation is:

Stop the SAP specific tuning of the system by 'reverting' the applied SAP solution or by stopping the daemon.

Change the system configuration by changing the /etc/security/limits file, by changing a value in the /sys or /proc filesystem,  by changing /etc/sysctl.conf file or by using the sysctl command (depends on which system parameter should be changed and if the change should be permanent or only temporarily).

Start the SAP specific tuning of the system again.

So in short:

#1
saptune solution revert HANA
    or
saptune daemon stop

#2
vi /etc/security/limits.conf
    or
vi /etc/sysctl.conf
    or
sysctl <parameter> <value>

#3
saptune solution apply HANA
    or
saptune daemon start

If things are not done in the correct order, it may appear that it is not possible to prevent manually set values being overwritten.

A short explanation about the files in /var/lib/saptune/saved_state:

saptune was designed to preserve the state of the system before starting the SAP specific tuning, so that it will be possible to restore that previous state should it be decided that the SAP specific tuning is no longer needed or should be changed.

This system state is saved during the 'apply' operation of saptune in the saptune internal used files in /var/lib/saptune/saved_state. The content of these files depends on the previous state of the system. If the current system settings/values are already in compliance with the defined values from a SAP Note or a SAP solution, then a save_state file is not written. If some of the values from a SAP note differ from the current system values, the state (values) of these parameters are saved to enable a revert operation (in case a revert should be actioned at a later time) and then the values from the SAP Note will be applied. If the values are applied by saptune, no further monitoring of the system parameters are done, so changes of saptune relevant parameters will not be observed. If a SAP Note or a SAP solution should be reverted, then first the values read from the /var/lib/saptune/saved_state files will be applied to the system to restore that saved system state and then the corresponding save_state file will be removed.

So when removing files from /var/lib/saptune/saved_state the knowledge about the previous system state is lost and the revert functionality of saptune will be unavailable. When changing system values while saptune has already applied the SAP Note values, these changes will be lost during the revert of the SAP Note settings (which is done during system reboot).

To see if your system is in compliance with a SAP Note or a SAP solution, or to see which values will be changed by saptune when applying a SAP Note or a SAP solution, you can use saptune with the options 'simulate' or 'verify', before actually applying the note or the solution.

e.g.
saptune solution verify HANA
    or
saptune solution simulate HANA
    or
saptune note verify 1275776