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SYS owned tables [Base tables of the Oracle dictionary]
These tables are the base tables in the data dictionary. Their content is exposed for easier access through SQL through the static dictionary views.
pname can take several values, the most usefull beeing:
This table allows to monitor the usage of predicates on columns in select statements.
It is updated (if _column_tracking_level is set to 1) at intervalls by smon, so it might be a little out of date.
Also, dbms_stats will make use of that info when deciding if it needs to create a histogram on a column.
This table keeps track of constraints. dba_constraints derive from this table.
This table stores a row for each lock allocated with dbms_lock.allocate_unique.
Lists all objects created in a database.
The following statement lists all objects created for the current loged on user:
This view lists the selecting user's privileges.
See also this page.
smon_scn_time is a table that is filled by SMON every 5 minutes with a timestamp and the current SCN. However, it only counts 1440 records (=5 days). This makes it possible to roughly find an SCN for a point in time in the last 5 days.
This table is not documented, so only look at it out of curiosity.
This table is important to store the history of passwords for a user if password related profiles are enabled.