Parallel Execution and useful views in Oracle

By default, parallel_max_servers is enabled if it is greater than 0.

Alter session enable parallel [ddl | dml | query];
Alter session disable parallel [ddl | dml | query];
Alter session force parallel ddl parallel 5;

Several views used to analyze DB performance.

V $ PROCESS
Contains information about the currently active processes

V $ SESSION
Lists session information for each current session

V $ SESS_IO
Contains I/O statistics for each user session

V $ SESSION_LONGOPS
Displays the status of varous operations that run for longer than 6 seconds (in absolute time ). these operations currently include existing backup and recovery functions, statistics gathering, and query execution. more operations are added for every Oracle Database release.

V $ SESSION_WAIT
Displays the current or last wait for each session

V $ SESSION_WAIT_HISTORY
Lists the last ten wait events for each active session

V $ WAIT_CHAINS
Displays information about blocked sessions

V $ SYSSTAT
Contains session statistics

V $ RESOURCE_LIMIT
Provides information about current and maximum global resource utilization for some system resources

V $ SQLAREA
Contains statistics about shared SQL areas. Contains one row for each SQL string. Provides statistics about SQL statements that are in memory, parsed, and ready for execution

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