Oracle ROWID Purpose Explained

In Oracle Database, ROWID is a unique identifier used to identify a record in a table. It is a string composed of the following components:

1. Data object ID: Identifies the physical location of a data object (table or index).
2. File number: identifies the data file containing data objects.
3. Block number: Identifies the position of a data object in a data file.
4. Line number: Indicates the position of a row within a data object.

There are several aspects to the function of ROWID:

1. The only identifier: ROWID can uniquely identify a record in a table, allowing for precise location of a specific record without the need for other search criteria.
2. Quick access: Because ROWID directly points to the physical location of the data file, it is possible to quickly locate a specific record in the table, thus improving access efficiency.
3. Data replication: ROWID can be used to copy data between different databases. With ROWID, specific records can be accurately specified for replication.
4. Forced row-level locking may be necessary in certain situations to lock a specific record in a table to prevent data inconsistency issues caused by concurrent access. The ROWID can be used to specify the record to be locked.

It is important to note that ROWID may change in some situations. For example, ROWID could change when the table is rebuilt, indexes are reorganized, or data is moved. Therefore, when using ROWID for data operations, it is important to be mindful of the potential impact of these changes.