Re: Need help with tuning import????

sjs_at_shell.portal.com (Schow) writes:
:
: Hey all,
:
: Big question for you. I have a table that is about 80 MB in size. IT
: contains a long raw column. When I export, it does the entire table
: in just a few minutes. When I import the table it takes 90 minutes.
: The table contains a long-raw column. Other tables take only minutes
: to import. So I am assuming it must have something to do with the
: long raw. But I am confused at this point as to why it takes so long
: and why it goes through this cyclic behavior of slowing down and speeding
: up during the import.....
:
: The dynamics of disk i/o are interesting--at the beginning of the import
: (about 5 minutes) we write about 350K/sec to both disks (redo logs and
: table). Then after about the 5 min mark, the i/o to the disk containing the
: table drops to a few K/sec often reaching zero for 20-30 seconds; meanwhile
: the i/o to the redo disk continues at the 350K/sec rate. Thereafter
: transfer rate for the table's disk goes back up to 350K/sec for a few
: seconds then drops back down to near zero. This pattern continues for the
: rest of the 80-90 minutes the import takes.
:
: Thanks in advance
:
:

Redo is constantly being written to the redo logs, hence the constant writing to this disk.

The inserted data is being written to blocks cached in the SGA. Hence no writing to this disk.

Every 20-30 seconds, a log switch occurs, causing a checkpoint. This causes all dirty blocks in the SGA to be written to disk, hence the disk activity. Received on Tue Jun 06 1995 - 00:00:00 CEST