How to make the mysql MEMORY ENGINE store more data?

Question

I want to alter a table from INNODB to MEMORY ENGINE.

So I typed this command:

alter table sns ENGINE=MEMORY;

Then the MySQL shows

Answer 1

The max size for the memory table is set on creation and altering and based on the max_heap_table_size value.

So when you want to raise the max size for an existing memory table you can change the max_heap_table_size and then apply it by altering the table to the same storage engine.

Example:

# Raise max size to 4GB
SET max_heap_table_size = 1024 * 1024 * 1024 * 4;

# If already a memory table, the alter will not change anything.
# Only apply the new max size.
ALTER TABLE table_name ENGINE=MEMORY;

Misunderstanding regarding tmp_table_size

The tmp_table_size variable only determines the max size for internal memory tables. Not user-defined.

As stated in the MySQL docs:

The maximum size of internal in-memory temporary tables. This variable does not apply to user-created MEMORY tables.