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Extending HCL OneDB™Beyond standard relational database objects, HCL OneDB™ can be extended to handle specialized data types, access methods, routines, and other objects. HCL OneDB™ includes many built-in extensions that are fully integrated in the database server. HCL OneDB™ 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 HCL OneDB™.
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 HCL OneDB™ databases.
DataBlade® API Function ReferenceThe HCL OneDB™ DataBlade® API Function Reference describes the DataBlade® API functions and the subset of functions that the DataBlade® API supports.
Function descriptionsThis section gives comprehensive reference information about the functions that are valid within DataBlade® API modules. It lists the function descriptions in alphabetical order, with syntax, usage information, and return values for the functions.
The mi_lo_lock() functionThe mi_lo_lock() function obtains a byte-range lock on the specified number of bytes in a smart large object.

The mi_lo_lock() function

The mi_lo_lock() function obtains a byte-range lock on the specified number of bytes in a smart large object.

Syntax

mi_integer mi_lo_lock(conn, LO_fd, offset, whence, nbytes, lock_mode)
   MI_CONNECTION *conn;
   MI_LO_FD LO_fd;
   mi_int8 *offset;
   mi_integer whence;
   mi_int8 *nbytes;
   mi_integer lock_mode;

conn

This value is one of the following connection values:

A pointer to a connection descriptor established by a previous call to mi_open(), mi_server_connect(), or mi_server_reconnect().

A NULL-valued pointer (database server only)

LO_fd

The LO file descriptor of the smart large object to lock.

offset

A pointer to the eight-byte integer (mi_int8) offset from the starting LO seek position that whence specifies.

whence

An integer value that identifies the starting LO seek position.

nbytes

A pointer to the eight-byte integer (mi_int8) that specifies the number of bytes to lock. This value cannot exceed 2 GB.

lock_mode

An integer constant that indicates the lock mode to use. Valid constant values are:

MI_LO_SHARED_MODE: Lock mode is shared mode.
MI_LO_EXCLUSIVE_MODE: Lock mode is exclusive mode.


Valid in client LIBMI application?	Valid in user-defined routine?
No	Yes

Usage

The mi_lo_lock() function requests a byte-range lock of the lock_mode type on the open smart large object that LO_fd indicates. This lock request applies to nbytes number of bytes beginning at the LO seek location that the whence and offset arguments specify.

By default, the database server locks the entire smart large object when you request a read or write operation. With the mi_lo_lock() function, you can request a byte-range lock, which allows transactions to lock only the required ranges of bytes in a smart large object. However, the smart large object on which you request the byte-range lock must have the byte-range locking feature enabled with the LO_LOCKRANGE storage-characteristic constant.

For more information about locks for smart large objects or about how to use byte-range locks, see the HCL OneDB™ DataBlade® API Programmer's Guide.

Server only: The mi_lo_lock() function does not need a connection descriptor to execute. If your UDR does not need a valid connection for other operations, you can specify a NULL-valued pointer for the conn parameter to establish a NULL connection. For information about the advantages of a NULL connection, see the HCL OneDB DataBlade API Programmer's Guide.

Return values

MI_OK: The function was successful; the requested lock was successfully obtained.
MI_ERROR: The function was not successful; the requested lock cannot be obtained or the smart large object has not been opened for byte-range locking.