For NVARCHAR2 and VARCHAR2 maximum size is 4000 bytes, or 32767 bytes if the MAX_STRING_SIZE initialization parameter is set to EXTENDED. This is useful you have to allocate more data to a variable.
If your Oracle database has Flashback enabled, you can query past versions of data within a specified retention period. Here’s how to use Flashback to retrieve a prior state of data:
SELECT *
FROM your_table AS OF TIMESTAMP (SYSTIMESTAMP - INTERVAL '5' MINUTE)
WHERE your_condition;
Replace SYSTIMESTAMP - INTERVAL '5' MINUTE with the timestamp or interval that reflects when the data was last known to be in its old state.
Note: Flashback must be enabled, and it’s only available within the Flashback retention window, which depends on your database configuration.
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