i have an RMAN restore going on since last night. fortunately the requirements are still on disk as duplication hasn't started yet. however, i noticed that the restore speed fluctuates. it was at 45KBps a few while ago and now it drops to 15KBps. but before posting this i noticed it went back up to 40-45 KBps.
what could be the reason? as i was expecting that since this is on disk it'll have a sustained restore speed.
11/08/2017 20:09:06 - begin Restore
11/08/2017 20:09:06 - Info bprd (pid=5727) Found (1) files in (1) images for Restore Job ID 619851.xxx
11/08/2017 20:09:07 - restoring from image ruh1erpdb1_1509904827
11/08/2017 20:09:07 - Info bprd (pid=5727) Searched (1) files of (1) files for Restore Job ID 619851.xxx
11/08/2017 20:09:07 - Info bprd (pid=5727) Restoring from copy 1 of image created Sun Nov 5 21:00:27 2017 from policy Daily_ruh1erpdb1
11/08/2017 20:09:07 - requesting resource @aaaan
11/08/2017 20:09:07 - granted resource MediaID=@aaaan;DiskVolume=PureDiskVolume;DiskPool=NBU-PureDisk-1;Path=PureDiskVolume;StorageServer=ovmmanager;MediaServer=ovmmanager
11/08/2017 20:09:08 - Info bpbrm (pid=5782) ruh1erpt2 is the host to restore to
11/08/2017 20:09:08 - Info bpbrm (pid=5782) reading file list for client
11/08/2017 20:09:08 - Info bpbrm (pid=5782) listening for client connection
11/08/2017 20:09:09 - Info bpbrm (pid=5782) accepted connection from client
11/08/2017 20:09:09 - Info dbclient (pid=26875) Restore started
11/08/2017 20:09:09 - Info bpbrm (pid=5782) bptm pid: 5795
11/08/2017 20:09:09 - Info bptm (pid=5795) start
11/08/2017 20:09:09 - started process bptm (pid=5795)
11/08/2017 20:09:09 - Info bptm (pid=5795) reading backup image
11/08/2017 20:09:09 - Info bptm (pid=5795) using 256 data buffers
11/08/2017 20:09:09 - Info bptm (pid=5795) spawning a child process
11/08/2017 20:09:09 - Info bptm (pid=5795) child pid: 5799
11/08/2017 20:09:10 - begin reading
11/08/2017 21:02:43 - Info bptm (pid=5795) waited for empty buffer 816 times, delayed 1371 times
11/08/2017 21:02:43 - end reading; read time: 0:53:33
11/08/2017 21:02:43 - begin reading
11/08/2017 23:04:54 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/08/2017 23:04:54 - end reading; read time: 2:02:11
11/08/2017 23:04:55 - begin reading
11/09/2017 01:01:46 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 01:01:46 - end reading; read time: 1:56:51
11/09/2017 01:01:47 - begin reading
11/09/2017 02:22:37 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 02:22:37 - end reading; read time: 1:20:50
11/09/2017 02:22:37 - begin reading
11/09/2017 05:13:01 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 05:13:01 - end reading; read time: 2:50:24
11/09/2017 05:13:02 - begin reading
11/09/2017 06:16:30 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 06:16:30 - end reading; read time: 1:03:28
11/09/2017 06:16:30 - begin reading
11/09/2017 07:03:44 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 07:03:44 - end reading; read time: 0:47:14
11/09/2017 07:03:45 - begin reading
11/09/2017 08:01:11 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 08:01:11 - end reading; read time: 0:57:26
11/09/2017 08:01:11 - begin reading
11/09/2017 09:33:13 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 09:33:13 - end reading; read time: 1:32:02
11/09/2017 09:33:14 - begin reading
11/09/2017 10:46:39 - Info bptm (pid=5795) waited for empty buffer 0 times, delayed 0 times
11/09/2017 10:46:39 - end reading; read time: 1:13:25
11/09/2017 10:46:40 - begin reading
11/09/2017 11:15:10 - Info bptm (pid=5795) waited for empty buffer 376 times, delayed 409 times
11/09/2017 11:15:10 - end reading; read time: 0:28:30
11/09/2017 11:15:10 - begin reading
