[_m3]

* The maximum size of a BLOB or TEXT object is determined by its type, but the largest value you can actually transmit between the client and server is determined by the amount of available memory and the size of the communications buffers. You can change the message buffer size, but you must do so on both the server and client ends. See section 13.2.4 Tuning Server Parameters.

shell> mysqld --help

This command produces a list of all mysqld options and configurable variables. The output includes the default values and looks something like this:

Possible variables for option --set-variable (-O) are:
back_log              current value: 5
bdb_cache_size        current value: 1048540
binlog_cache_size     current_value: 32768
connect_timeout       current value: 5
delayed_insert_timeout  current value: 300
delayed_insert_limit  current value: 100
delayed_queue_size    current value: 1000
flush_time            current value: 0
interactive_timeout   current value: 28800
join_buffer_size      current value: 131072
key_buffer_size       current value: 1048540
lower_case_table_names  current value: 0
long_query_time       current value: 10
max_allowed_packet    current value: 1048576
max_binlog_cache_size current_value: 4294967295
max_connections       current value: 100
max_connect_errors    current value: 10
max_delayed_threads   current value: 20
max_heap_table_size   current value: 16777216
max_join_size         current value: 4294967295
max_sort_length       current value: 1024
max_tmp_tables        current value: 32
max_write_lock_count  current value: 4294967295
myisam_sort_buffer_size  current value: 8388608
net_buffer_length     current value: 16384
net_retry_count       current value: 10
net_read_timeout      current value: 30
net_write_timeout     current value: 60
query_buffer_size     current value: 0
record_buffer         current value: 131072
slow_launch_time      current value: 2
sort_buffer           current value: 2097116
table_cache           current value: 64
thread_concurrency    current value: 10
tmp_table_size        current value: 1048576
thread_stack          current value: 131072
wait_timeout          current value: 28800

If there is a mysqld server currently running, you can see what values it actually is using for the variables by executing this command:

shell> mysqladmin variables