Deep stand-alone transactions

The ACDI of the transaction
1. atomicity (one transaction either succeeds at the same time and fails at the same time)
Bob gave Smith 100 dollars.
Important: Atomicity only records the Undo log, which can be rolled back to the previous version.
2, consistency (add a lock to the transaction)
Core: Can (happen before)
3, Isolation (performance for the reason, the destruction of consistency)
1. Serialized read-Write
Exclusive Lock: (only one transaction has him in a unit of time)
Read/write Lock:
2, (Repeatable READ: (read lock can not be written lock upgrade) read and read parallel)
3, (Read Committed: (read lock can be write lock upgrade) Read and read parallel, read and write parallel (read not yet))
4, (READ UNCOMMITTED: (write lock, read without lock) read and read parallel, reading and writing parallel, write read parallel (write not))

4. Persistence: After the transaction is completed, the transaction is committed and saved in the database.

The standard is not necessarily equal to the right.

Is there any possibility of parallel writing?

Deep stand-alone transactions