Will the
application run faster or slower? In general, it will run slower because the throughput of the single
disk is unlikely to be equal to the combined throughput of the eight separate disks. Rather than
designing your disk layout based on the space available (a common method), design it based on
the throughput of the disks available. You may decide to use only part of each disk. The remaining
space on the disk will not be used by the production application unless the throughput available
for that disk improves.
Avoid the Use of the Temporary Segments
Whenever possible, perform all sorts in memory. Any operation that writes to the temporary
segments is potentially wasting resources. Oracle uses temporary segments when the SORT_
AREA_SIZE parameter (or PGA_AGGREGATE_TARGET, if it is used) does not allocate enough
memory to support the sorting requirements of operations. Sorting operations include index
creations, order by clauses, statistics gathering, group by operations, and some joins. As noted
earlier in this chapter, you should strive to sort as few rows as possible. When performing the
sorts that remain, perform them in memory.
Favor Fewer, Faster Processors
Given the choice, use a small number of fast processors in place of a larger number of slower
processors. The operating system will have fewer processing queues to manage and will generally
perform better.
Divide and Conquer Your Data
If you cannot avoid performing expensive operations on your database, you can attempt to split
the work into more manageable chunks.
Pages:
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239