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Extending Informix®
Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix includes many built-in extensions that are fully integrated in the database server. Informix also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix.
Informix® extensions and DataBlade® modules
These topics describe how to use built-in database extensions and separately installed DataBlade® modules.
Database Extensions User's Guide
The Informix® Database Extensions User's Guide explains how to use the database extensions that come with HCL Informix: Large Object Locator, MQ messaging, binary data types, basic text search, node data type, and SQL packages.
SQL Packages Extension
The SQL packages extension provides SPL routines that you can use in an application that is compatible with database servers other than Informix®.
DBMS_LOB package
The DBMS_LOB package provides the capability to operate on large objects.
SUBSTR function
The SUBSTR function provides the capability to return a portion of a large object.

Extending Informix®
Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix includes many built-in extensions that are fully integrated in the database server. Informix also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix.
- Informix® extensions and DataBlade® modules
  These topics describe how to use built-in database extensions and separately installed DataBlade® modules.
  - Database Extensions User's Guide
    The Informix® Database Extensions User's Guide explains how to use the database extensions that come with HCL Informix: Large Object Locator, MQ messaging, binary data types, basic text search, node data type, and SQL packages.
    - Large object management
      The Large Object Locator extension enables you to create a single consistent interface to large objects. It extends the concept of large objects to include data stored outside the database.
    - MQ Messaging
      WebSphere® MQ (WMQ) messaging products provide an infrastructure for distributed, asynchronous communication of data in a distributed, heterogeneous environment. The WMQ message queue allows you to easily exchange information across platforms.
    - Binary data types
      The binary18 and binaryvar data types allow you to store binary-encoded strings, which can be indexed for quick retrieval.
    - Basic Text Search
      You can perform basic text searching for words and phrases in a document repository stored in a column of a table.
    - Hierarchical data type
      The node data type helps to resolve a difficult relational database problem–transitive closure.
    - SQL Packages Extension
      The SQL packages extension provides SPL routines that you can use in an application that is compatible with database servers other than Informix®.
      - DBMS_ALERT package
        The DBMS_ALERT package provides a set of procedures for registering for alerts, sending alerts, and receiving alerts.
      - DBMS_LOB package
        The DBMS_LOB package provides the capability to operate on large objects.
        APPEND procedures
        The APPEND procedures provide the capability to append one large object to another.
        COMPARE function
        The COMPARE function performs an exact byte-by-byte comparison of two large objects for a given length at given offsets.
        COPY procedures
        The COPY procedures provide the capability to copy one large object to another.
        ERASE procedures
        The ERASE procedures provide the capability to erase a portion of a large object.
        GETLENGTH function
        The GETLENGTH function returns the length of a large object.
        INSTR function
        The INSTR function returns the location of the nth occurrence of a specified pattern within a large object.
        READ procedures
        The READ procedures provide the capability to read a portion of a large object into a buffer.
        SUBSTR function
        The SUBSTR function provides the capability to return a portion of a large object.
        TRIM procedures
        The TRIM procedures provide the capability to truncate a large object to the specified length.
        WRITE procedures
        The WRITE procedures provide the capability to write data into a large object.
      - DBMS_OUTPUT package
        The DBMS_OUTPUT package provides a set of procedures for putting messages (lines of text) in a message buffer and getting messages from the message buffer. These procedures are useful during application debugging when you need to write messages to standard output.
      - DBMS_RANDOM package
        The DBMS_RANDOM package provides a mechanism for generating random numbers. Use the INITIALIZE procedure to set the seed value, which is used by the random number generator to generate the numbers.
      - UTL_FILE package
        The UTL_FILE package provides a set of routines for reading from and writing to files on the database server file system.
    - Regex pattern matching
      Regular expressions combine literal characters and metacharaters to define the search and replace criteria. You run the functions from the Informix® Regex extension to find matches to strings, replace strings, and split strings into substrings.
  - Performing XML Publishing
    The Informix® XML User's Guide includes information about using built-in functions for XML publishing with Informix.
  - Spatiotemporal Search for Moving Objects User's Guide
    The describes how to program applications to search data from moving objects in HCL Informix® databases using the spatiotemporal search extension.
  - TimeSeries Data User's Guide
    The Informix® TimeSeries Data User's Guide contains information to assist you in using the TimeSeries extension with HCL Informix.
  - Web DataBlade Module
    Use the Web DataBlade® module to create web applications that incorporate data that is retrieved dynamically from the HCL Informix® database.
- Creating extensions
  You can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.

SUBSTR function

The SUBSTR function provides the capability to return a portion of a large object.

The function returns a BLOB(32767) (for a BLOB) or VARCHAR (for a CLOB) value for the returned portion of the large object read by the function.

Syntax

SUBSTR(lob_loc [ ,amount [ ,offset ] ] )

Parameters

lob_loc: An input argument of type BLOB(10M) or CLOB(10M) that specifies the large object locator of the large object to be read.
amount: An optional input argument of type INTEGER that specifies the number of bytes or characters to be returned. The default value is 32,767.
offset: An optional input argument of type INTEGER that specifies the position within the large object to begin returning data. The first byte or character is at position 1. The default value is 1.