Hello.
I have site on nginx1.10.3 wich reads from db a lot of records, makes an ordering with php7.3-fpm and then served to the public.
Records are quite few and I would like to give it more memory so as to perform better.
I dont know where this extre memory should be given. To nginx or to php7.3-fpm?

any help is appreciated.

Curious, but i just wanted to ask nearly the same.
Different sites say, that you must do following:

For individual website/php-pool/vhost:
- Change it in the php.ini
- Change it in www.conf (php-pool)
- Change it in the nginx-vhost-file

For global (all) the same except the last. There you must edit the main nginx.conf instead.

I dont understand, why you must edit it in the php-pool-file AND in the vhost-file.
My vhost uses a specific pool-file, so i just added the following there:
"php_admin_value[memory_limit] = 1024M"
and thats it. I've tested it and it works!

So i would ask, can anyone explain me, why i should edit the vhost and php.ini too?

Well I am quite new. I think pool configures how php works with an nginx request. So I guess if there is an php intesive script you increase memory at the pool.
But as I said I am not an expert. I hope some more expertize to answer.