OCLA enables the user to tell which instructions each Alpha EV7
    CPU has executed by setting aside one seventh of the Alpha EV7
    cache as acquisition memory which stores the virtual addresses
    of instructions executed by the Alpha EV7 CPU. The acquisition
    memory in the cache can later be analyzed with an SDA extension.

    The acquisition of instructions can be enabled or disabled
    while the system is running, thereby allowing the acquisition
    of instruction streams for a given period of time without the
    need to restart the system.

    If the OCLA is enabled and started, and your system subsequently
    fails due to a crash, the current acquisition memory is
    automatically saved to the system dump file. The instructions
    executed by each CPU prior to the system failure can then be
    analyzed with SDA. Upon restart of the system, the acquisition
    memory in the EV7 is still there and can be copied into system
    memory using the OCLA ENABLE and OCLA DUMP commands.

    If the STOP/CPU command is issued on a CPU for which OCLA has
    been enabled, OCLA is automatically disabled if the CPU is
    allowed to leave the active set. When a CPU is started with the
    START/CPU command, OCLA is not automatically enabled; rather, it
    must be enabled using SDA.