Oracle parallel transaction Rollback related parameters and views

/****** Related Parameters ****/
Fast_start_parallel_rollback
1. There are 3 kinds of values: False,low,high
2. Value Meaning: False---Disable the parallel rollback feature
Low---Parallel rollback max is 2*cpu_count
High---Parallel rollback maximum is 4*cpu_count
3. This parameter applies to parallel DML or parallel DDL that was not completed before system crash
4. Determine the degree of parallelism for parallel rollback
5. This parameter applies the rollback phase after the roll-forward is completed for the undo block operation

/****** related views ****/
V$fast_start_servers
1. View the working status of a recovery subprocess that implements parallel transaction recovery
2. Sub-process status: idle,recovering
Number of Undo Block applied
Transaction ID
Process ID of the child process

V$fast_start_transactions
Review the progress of the recovery several important columns:
USN--Recovery transaction undo segment Number
State---Restore the status of the transaction: recovery complete, not recovered
The process ID of the PID---recovery transaction
Udnoblocksdone-Number of undo blocks applied
Undoblockstotal--Total number of undo blocks
XID---transaction ID
Parentusn--undo segment number for the parent transaction of the parallel DML transaction

/****** related sql****/
Select
Undoblockstotal "Total",
Undoblocksdone "Done",
Undoblockstotal-undoblocksdone "ToDo",
To_char (sysdate, ' yyyy-mm-dd hh24:mi:ss ')
From V$fast_start_transactions;

Oracle parallel transaction Rollback related parameters and views