What is the meaning of "available RAM" for calculating MySQL max_connections

Question

The question was asked previously, "how do I calculate MySQL max_connections" and this was the answer:

max_connections = (Available RAM - Global Buffers) / Thread Buffers

Since I don't have enough reputation to add a comment to the existing question I had to ask a brand new question.

I can get the buffer values by executing : SHOW VARIABLES LIKE '%buffer%'; but what is the available RAM part of this equation exactly?

Is this value in bytes, kilobytes, megabytes? Something else? Also, do I use the available RAM shown in the resource monitor while my site is being used, or do I need to use the total amount of RAM installed on the machine?

Answer 1

I'd say 'Available RAM' means max memory mysql can claim. And 'Global buffers' would mean buffers like innodb_buffer_pool, key_buffer_size, query_cache_size, etc.

Answer 2

At this time you can use mysqlcalculator.com to assist with determining your RAM footprint in about 2 minutes if you have your SHOW GLOBAL VARIABLES; list available.

Answer 3

The default of 151 is a reasonable starting point. After running for some time, you may, but probably won't, see any problems. If you do have problems, any of several things could need tweaking -- including indexes on tables. max_connections rarely needs tweaking.

Bottom line: Don't fret over that one settings.

Answer 4

Hi When I give the values in the above formula, I am getting -ve DB Connections kindly adivice. Using 5.7 mysql