The DBA can also limit the amount of expansion
for a given datafile by using the MAXSIZE parameter. In any case, the size of the datafile is
ultimately limited by the disk volume on which it resides.
FIGURE 1-3 Oracle physical storage structures
26 Oracle Database 11g DBA Handbook
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The DBA often has to decide whether to allocate one datafile that
can autoextend indefinitely or to allocate many smaller datafiles with
a limit to how much each can extend. Although the performance of
each solution is likely very similar, it is probably a better idea to stick
with more datafiles that are each less than 2GB in size. It is a lot easier
to move around relatively smaller files, and some file systems may
limit the size of an individual file to 2GB anyway. Also, if you need to
temporarily move all the datafiles for a tablespace to another server,
it is often easier to find several volumes, each with enough space to
hold one of the datafiles, rather than one volume with enough space
to hold a single datafile that is 25GB.
The datafile is the ultimate resting place for all data in the database. Frequently accessed
blocks in a datafile are cached in memory; similarly, new data blocks are not immediately written
out to the datafile but rather are written to the datafile depending on when the database writer
process is active. Before a user??™s transaction is considered complete, however, the transaction??™s
changes are written to the redo log files.
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