• A Full Table Scan, e.g. TABLE ACCESS FULL phrase, found in the Explain Plan usually indicates an inefficient access path. This means that the only way the database found to get to the desired data is by reading every single row in the table.

• Notice that if the logic indeed requires reading all data, then this database decision is indeed correct. However, if you intended to get a small subset of rows from a large table and ended up reading all of it this is definitely not efficient and should be fixed. If this is the case, try and find a better SQL structure that would avoid a full table access. If you can't find such, please consult a DBA as this SQL may require an additional Index to be created for the table.

• Sometimes there would be a proper index on a particular table but still a full table scan would be chosen for the access path of that table. This may be as result of an inefficient Join Order. Please see details below.