Unindexed FK
ON DELETE CASCADElocks child table- Join from child to parent
Killing session:
- status = ‘terminated’ if rollback > 1 min
IMMEDIATE-> return to user after kill without waiting for completion or time-out of 1 min
18C+ ALTER SYSTEM CANCEL
SQL <sid>,<serial>[,@<instance>][,<sql_id>]
ORA-54 DDL_LOCK_TIMEOUT