So you need to read an entire table? Here’s some features and techniques that may help.
Employ Parallelism: Ah, the sweetest technique of all. Brute force. If you have the resources, then let Oracle divide the table into chunks and use all your system resources to scan it. Unfriendly in an OLTP environment, mind you.
Compress Data Segments: Make the table smaller! Block level compression can shrink that data like a plunge into cold water. Very OLTP unfriendly.
Reduce Free Space Percent: PCTFREE = very small => more rows per block => smaller table. And potentially a higher chance of row migration, of course.
Increase Percent Used: PCTUSED = large => less likely that blocks retain free space following deletes => more rows per block => smaller table.
Use a Larger Block Size: For significantly long rows you may get reduced empty space, thus a smaller table to scan.
Reorder The Columns: If you are commonly interested in just a subset of columns (for example metrics in a fact table) then consider making them the first columns of the table definition – for tables with lots of columns there is measurable overhead in finding the end columns (I’m not talking about row chaining here). Hmmm, maybe I’ll post something else about this.
Index Columns of Interest: An index can be treated as a skinny table, and your query might be satisfied by a fast ful or full index scan. The usual comments about NULL values in indexes apply here. Don’t neglect consideraton of index size either – index key compression and use of bitmap indexes provide smaller structures to scan.
Materialized Views: Is there anything they’re not good for? This could be a genuine skinny table, or an aggregation of selected columns.
Ensure Table Is Spread Over Available Devices: With consequent reduced likelihood of encountering an i/o choke point.
There is not a single feature listed here that carries with it no disadvantages, and depending on your circumstances the severity of the disadvantages may range from the insignificant to the devastating.
Do not implement any of these without understanding how the feature works, the mechanism by which it provides the advantage, how it brings disadvantages, and how these all interact in your particular situation.