What parameters to put in sysctl, on the database server?

Question

linux

Good afternoon!
There is a database server - Firebird 1.5. On board Debian and Centos - x86, because FB 1.5 is only x86
So it turns out that the memory is delivered from the time the OS was installed.
Question about memory settings. I added up to 48GB of memory.
wrote parameters
#SHMMAX this is the maximum allocated in one request - this is the actual amount of memory (as opposed to pages). For example, for 4 GB it will be: kernel.shmmax = 4294967296
kernel.shmmax=51111792640 #For
8gb it is kernel.shmall = 8000x1024x1024/4096 or kernel.shmall = 2097152
kernel.shmall=12288000
##kernel.sem=
kernel.sem= 250 256000 256 1024
Then it turns out like this:
sysctl -p
error: ":kernel.shmmax" is an unknown key
kernel.shmmax = 51111792640
kernel.shmall = 12288000
kernel.sem = 250 256000 256 1024
vm.swappiness = 0
error: ":kernel.shmmax" is an unknown key
why unknown key ?
Do I need to edit something or comment out everything and reboot so that he himself registers everything?
How to understand how to count?
read according to this manual
https://www.ibm.com/support/knowledgecenter/ru/SSE...