Why am I getting the ORA-00381 error when initializing the parameter?

DB_BLOCK_BUFFERS, BUFFER_POOL_KEEP, and BUFFER_POOL_RECYCLE

The new parameters to size the buffer cache components are:

DB_CACHE_SIZE, DB_KEEP_CACHE_SIZE, and DB_RECYCLE_CACHE_SIZE

You cannot mix and match these parameters. I would bet that you set DB_KEEP_CACHE_SIZE and also have DB_BLOCK_BUFFERS set. As the ORA-381 error states, you cannot use the old parameters with the new ones. So, change DB_BLOCK_BUFFERS to DB_CACHE_SIZE (but keep in mind that the old parm denotes the number of blocks, and the new parm denotes the number of bytes, so you will have to perform some conversion here).