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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®.
Creating extensionsYou 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.
Virtual-Table Interface GuideThe Informix® Virtual-Table Interface Programmer's Guide explains how to create a primary access method with the Virtual-Table Interface (VTI) so that users have a single SQL interface to HCL Informix® tables and to data that does not conform to the storage scheme of HCL Informix®.
Descriptor function referenceThese topics provide the syntax and usage for the functions that the HCL Informix® database server supplies to access-method developers.
Accessor functionsThe Virtual-Table Interface (VTI) library contains functions that primarily access selected fields from the various descriptors.
The mi_scan_locktype() accessor functionThe mi_scan_locktype() function retrieves the lock type that the database server expects for the table that am_getnext scans.

The mi_scan_locktype() accessor function

The mi_scan_locktype() function retrieves the lock type that the database server expects for the table that am_getnext scans.

Syntax

MI_LOCK_TYPE mi_scan_locktype(MI_AM_SCAN_DESC *scanDesc);

scanDesc: Points to the scan descriptor.

Usage

If the access method supports locking, use the return value from this function to determine whether you need to lock an object during am_getnext.

Return values

MI_LCK_S: Indicates a shared lock on the table.
MI_LCK_X: Indicates an exclusive lock on the table.
MI_LCK_IS_S: Indicates an intent-shared lock on the table and shared lock on the row.
MI_LCK_IX_X: Indicates intent-exclusive lock on the table and exclusive lock on the row.
MI_LCK_SIX_X: Indicates an intent-shared exclusive lock on the table and an exclusive lock on the row.

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