oracle : any version
Oracle replication slows down insert , delete and update statements
If you setup a oradebug trace monitoring a oracle session
where insert statements run against a replicated table,
you can see statements like :
...
update "SYSTEM"."DEF$_AQCALL" set dscn = :1, cscn = :2
...
Every insert statement generates an update statement
You can find information about oradebug here