database table write on read

We have observed some file write activty by Oracle which we don't understand. We've replicated the situation on a test system as follows:

We insert a few rows which have a long raw column with 64000 bytes in it. After waiting several minutes (in which the rows seem to be successfully logged and written to the database) we retrieve any value from one of the rows.

The retrieval results in write activity to the table. This is documented by "select * from v$filestat" as well as AIX's iostat; The number of blocks written is the same as the number of database blocks included in all the rows inserted.

Can anyone tell us why this write activity occurs?

BTW, the 'extra' writing does not occur if we place 6K or less in the long raw column. It also does not occur on subsequent retievals -- only the first.

More details:

 Oracle Version 7.3.3
 AIX Version 4.2.1
 Database block size 16384

Thanks,

Duane Tiemann
Prodigy Services Co.
duanetiemann_at_prodigy.net Received on Wed Jul 22 1998 - 18:23:55 CDT