Introducing LONG-to-LOB Migration

To assist you in migrating to LOBs, Oracle supports the LONG API for LOBs. This API ensures that when you change your LONG columns to LOBs, your existing applications will require few changes, if any.

The term, "LONG API", refers to DML and querying of LONG datatypes. Examples of the LONG API are:

• For OCI: OCIBindByName(), OCIBindDynamic(), OCIDefineByPos(), OCIDefineDynamic(),....

• For PL/SQL: substr, instr,... and parameter passing

  Note: The "LONG API" applies to other datatypes besides LONGs. In this chapter, however, we are specifically interested in this API for LOBs. We refer to it here as the "LONG-to-LOB API".

Oracle9i supports LONG as well as LOB datatypes. When possible, change your existing applications to use LOBs instead of LONGs because of the added benefits that LOBs provide. See Chapter 7, "Modeling and Design", "LOBs Compared to LONG and LONG RAW Types".

This chapter describes how the "LONG API" referred to here as "LONG-to-LOB API", is used for LOBs.

Note: The performance of some LOB operations improves with the LONG-to-LOB API. See "Performance" for details.

Using the LONG-to-LOB API Results in an Easy Migration

LONG-to-LOB migration allows you to easily migrate your existing applications that access LONG columns, to use LOB columns. The migration has two parts:

• Data migration. This consists of the procedure to move existing tables containing LONG columns to use LOBs. This is described in "Migrating Existing Tables from LONG to LOBs" .

• Application migration. This specifies how existing LONG applications will change for using LOBs. Your application will only need to change in very rare cases. The LONG-to-LOB API that is implemented for LOBs is described in "Using LONG-to-LOB API with OCI" and "Using SQL and PL/SQL to Access LONGs and LOBs" .

  Note: LONGs have various restrictions, such as, there can be at most, only one LONG column in a table,.... On the other hand, LOBs do not have such restrictions. After you migrate your LONG tables to use LOBs, you will no longer have these LONG restrictions. You can have multiple LOB columns in a table, and do multiple >4k binds in a single INSERT/UPDATE,...