Indirect Chunk Operations in Client/Server Environments

When attempting a Get Direct/Chunk operation (23), your application may receive a Status Code 62. You may find that your application is specifying the Indirect Random Descriptor option (Subfunction 0x80000001), but with tracing enabled, you can see that the MicroKernel is actually receiving a Direct Random Descriptor option (Subfunction 0x80000000).

The indirect chunk option allows an application to specify a pointer to a data address in the application's memory block where the data should be stored after it is retrieved, rather than having the data returned in the actual Data Buffer parameter of the Btrieve call. However, since the application is running in an environment in which the MicroKernel does not have direct access to the application's memory, the Btrieve client Requester must convert indirect chunk requests into direct chunk requests before sending the request to the MicroKernel.

All applications always use interprocess communication (IPC) to communicate between the application and the MicroKernel. Since IPC is required, the MicroKernel has no access to the application's memory, so the client Requester must allocate a single contiguous block of memory and adjust all data pointers to point into that memory block. On return from the MicroKernel, the Requester converts the Data Buffer back into the appropriate format for the indirect option and moves the returned data chunk into the designated, indirect address in the application's memory block.