Long checkpoint time with HDR

Hi all, Our Server configure HDR. Before the 10-day holiday, checkpoint time was 0 second. While the holiday, the server was power-off. After the holidays, we did a test and restore database with ontape -r & -p. Now, the checkpoint time become 3~6 second, the server got worse performance But we didn't increase any process. And did a test for network with rcp 200MB file, the network was normal. We change the server to standard mode without HDR. The checkpoint time was 0 second , it was normal again. Why the checkpoint become longer with HDR?? IDS: 7.31.UD3 OS : AIX 5.1 2 CPU onconfig: PHYSFILE 102400 LOGFILES 80 LOGSIZE 4096 MULTIPROCESSOR 1 NUMCPUVPS 2 BUFFERS 128000 NUMAIOVPS 32 PHYSBUFF 128 LOGBUFF 32 CLEANERS 64 CKPTINTVL 89 LRUS 32 LRU_MAX_DIRTY 8 LRU_MIN_DIRTY 4 OPTCOMPIND 1 onstat -F:Fg Writes LRU Writes Chunk Writes 0 0 119789 onstat -R:707 dirty, 127992 queued, 128000 total, 131072 hash buckets, 4096 buffer size start clean at 8% (of pair total) dirty, or 320 buffs dirty, stop at 4% 0 priority downgrades, 0 priority upgrades