Oracle BLOB CLOB storage overhead

Oracle Tips by Burleson Consulting

Question:

How much overhead is required to store a BLOB or CLOB in Oracle?

Answer:

If you store a BLOB or CLOB off-line as a BFILE (on your file system directory) then there is no extra space overhead except for a tiny amount within Oracle to store the file locator.

If you choose to store a BLOB in-line (within an Oracle table), then you can set your tablespace and data file characteristics to minimize disk storage overhead.

I recommend storing BLOB types inside the Oracle tablespace because you have more control over the data for backups, recovery and data integrity. When storing a large BLOB inside an Oracle data file, you should consider a 32k blocksize (to avoid chaining) and carefully set pctfree and pctused to minimize wasted space within the Oracle data blocks.

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