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Lesson 10

Query Modify LOBs Conclusion

By now, you should understand the techniques to query and modify LOBs, and you should be able to:
  1. Create object tables with LOB as its data type
  2. Insert, update, and delete records from object tables that have the LOB data type
  3. Load data into object tables with LOBs using SQL*Loader
The following new features are available within LOBs for Oracle 8i:
  1. SQL*Loader can be used to load the data into LOBs.
  2. Oracle8i supports the creation, freeing, access, and update of temporary LOBs. Their default lifetime is a session, but they may be explicitly freed sooner by the application. They are ideal as transient workspaces for data manipulation: Because no logging is done orredo records are generated, they have better performance than persistent LOBs.
  3. A new conversion function, TO_LOB, can be used to convert a LONG into a LOB.
  4. Usable LOB chunk size is exposed to users via OCI and within DBMS_LOB.
  5. Open/Close/IsOpen Application Programming Interfaces (APIs) (OCI or DBMS_LOB) for internal LOBs have been added.
  6. Variable-width character sets are supported for CLOBs and NCLOBs.
  7. A DBMS_LOB and an OCI are provided to allow users to append data to the end of the LOB value.

As you have just learned, this is a lot of new functionality.


In this module, you were introduced to the following glossary terms:
  1. BLOB- Binary Large Objects, a LOB whose value is composed of unstructured binary
  2. CLOB: Character Large Object, a LOB whose value is composed of character data that corresponds to the database character set defined for the Oracle8 database.
  3. DBMS_LOB: The DBMS_LOB package provides subprograms to operate on BLOBs, CLOBs, NCLOBs, BFILEs, and temporary LOBs. You can use DBMS_LOB to access and manipulate specific parts of a LOB or complete LOBs.
  4. LOB: Large Objects are data types defined within Oracle 8i. They are used for storing upto 4 GB of data.
  5. LOBFiles: LOBFILES are relatively simple datafiles that facilitate LOB loading. The attribute that distinguishes LOBFILEs from the primary datafiles is that there is no concept of a record within LOBFILES.
  6. NCLOB: National Character Large Object, a LOB whose value is composed of character data that corresponds to the national character set defined for the Oracle8 database.
  7. OCI: Oracle Call Interface. The general goal of an OCI application is to operate on behalf of multiple users. Within an n-tier configuration, multiple users send HTTP requests to the client application. The client application may need to perform some data operations that include exchanging and performing data processing.
  8. Secondary Data Files: Secondary-Data-File are files similar in concept to the primary datafiles. Like primary datafiles, SDFs are a collection of records and each record is made up of fields. The SDFs are specified on a per control-file-field basis.
  9. SQL*Loader: This is a utility provided by Oracle to load data from text files into the Oracle database.
  10. Tablespace: A database is divided into logical storage units called tablespaces, which group related logical structures together. For example, tablespaces commonly group all the objects of an application to simplify some administrative operations.
  11. Zero-Byte Fillers: While editing or copying on an existing LOB, if the data already exists at the start position of the destination, it is overwritten with the source data. If the start position of the destination is beyond the end of the current data, zero-byte fillers (for BLOBs) or spaces (for CLOBs) are written into the destination LOB from the end of the current data to the beginning of the newly written data from the source.
In the next module, you will learn how to create methods for objects.