DB Recovery takes a long time even after checkpointing

Question

We observe that DB recovery takes a long time after application recovery even if we keep doing checkpoints at frequent(30 secs) intervals. These are the parameters that we use to open the environment:
env_flags =
DB_CREATE | /* Create the environment if it does not exist */
DB_RECOVER | /* Run normal recovery. */
DB_INIT_LOCK | /* Initialize the locking subsystem */
DB_INIT_LOG | /* Initialize the logging subsystem */
DB_INIT_TXN | /* Initialize the transactional subsystem. This
* also turns on logging. */
DB_INIT_MPOOL | /* Initialize the memory pool (in-memory cache) */
DB_THREAD | /* Cause the environment to be free-threaded */
DB_REGISTER |
DB_INIT_REP | /* Cause the environment to be replicated */
DB_SYSTEM_MEM ;
Our understanding was that recovery time should be proportional to the checkpoint interval. Can anyone please give some insights into what might be happening and how the recovery process works. It seems like DB is going back far in time while traversing the logs. We do not remove any log files as part of our regular process flows.
Secondly, we observe that recovery times increase proportionately with the size of our database even with checkpointing. Any insights into this are also welcome.
We are using DB 4.7.25 C API on HP-UX 11i.

Answer 1

try to burn recovery dvds and use it.
also perform disk check.
http://support.microsoft.com/kb/315265