Show innodb engine status tuning db server (2 replies)

I am new to dealing with the innodb engine status.

I also notice a number of these

TRANSACTION 0 6929906, not started, process no 1402, OS thread id 140010566186752\n
MySQL thread id 28, query id 475745 \n--------\n


I am not too sure with I/O section. As below is sample of my output.

FILE I/O\n--------\n
I/O thread 0 state: waiting for i/o request (insert buffer thread)\n
I/O thread 1 state: waiting for i/o request (log thread)\n
I/O thread 2 state: waiting for i/o request (read thread)\n
I/O thread 3 state: waiting for i/o request (write thread)\n
Pending normal aio reads: 0, aio writes: 0,\n ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0\n
Pending flushes (fsync) log: 0; buffer pool: 0\n9705 OS file reads, 16082 OS file writes, 8524 OS fsyncs\n
0.00 reads/s, 0 avg bytes/read, 5.14 writes/s, 2.00 fsyncs/s\n-------------------------------------\n

Why is it having so many transaction not started? What else can I look from this show engine to tune my db server?