This article was previously published under Q149429
For every custom control file (.OCX) that Visual Basic uses, there is anaccompanying .OCA file of the same file name. For example, GRAPH16.OCX hasan accompanying .OCA file called GRAPH16.OCA. An .OCA file is a binary filethat functions as both an extended type library file and a cache for thecustom control file.
A type library is a file or component within another file that contains OLEAutomation standard descriptions of exposed objects, properties, andmethods. The actual working type library for a custom control used inVisual Basic is a combination of the type library of the control itself andthe additional properties provided by the framework that wrap the control.
Some of the properties of the control are provided by the framework andsome by the control itself. Programmatically, the properties from theframework and the control all appear as properties of the control.
In order for these properties to appear, Visual Basic creates an extendedtype library when the control is loaded into the toolbox. Because theprocess of reading the control's type library and creating the extendedtype library is time consuming, Visual Basic caches the extended typelibrary information into an OCA file.
If you delete the OCA file for a control Visual Basic recognized, VisualBasic will recreate the .OCA file when you load a project requiring thecontrol. This recreation process comes with a time penalty.