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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_try_lock_memory() functionThe mi_try_lock_memory() function requests a lock on a named-memory block specified by name and memory duration.

The mi_try_lock_memory() function

The mi_try_lock_memory() function requests a lock on a named-memory block specified by name and memory duration.

Syntax

mi_integer mi_try_lock_memory(mem_name, duration)
   mi_string *mem_name;
   MI_MEMORY_DURATION duration;

mem_name

The null-terminated name of the named-memory block to lock.

duration

A value that specifies the memory duration of the named-memory block to lock. Valid values for duration are:

PER_ROUTINE: For the duration of one iteration of the UDR
PER_COMMAND: For the duration of the execution of the current subquery
PER_STATEMENT (Deprecated): For the duration of the current SQL statement
PER_STMT_EXEC: For the duration of the execution of the current SQL statement
PER_STMT_PREP: For the duration of the current prepared SQL statement
PER_TRANSACTION: For the duration of one transaction
PER_SESSION: For the duration of the current client session
PER_SYSTEM: For the duration of the database server execution


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

Important: This advanced function can adversely affect your UDR if you use the function incorrectly. Use it only when no regular DataBlade® API function can perform the task you need done.

Usage

The mi_try_lock_memory() function requests a lock on the named-memory block based on its memory duration of duration and its name, which mem_name references. The function does not wait until this lock has been obtained before it returns control to its calling function. If some other process currently holds a lock on the memory, mi_try_lock_memory() returns a status of MI_LOCK_IS_BUSY. The calling code can call mi_try_lock_memory() in a loop until the function returns the MI_OK status.

Important: After you obtain a lock on a named-memory block, release it as soon as possible. You must explicitly release a named-memory lock with the mi_unlock_memory() function.

Return values

MI_OK: The function successfully locked the specified named-memory block.
MI_NO_SUCH_NAME: The requested named-memory block does not exist.
MI_LOCK_IS_BUSY: The acquisition of a lock on the specified named-memory block failed because it is locked by another process.
MI_ERROR: The function was not successful.