Veritas Storage Foundation 5.1 SP1: Storage and Availability Management for Oracle (5900-1504, April 2011)

■ AWR file stats are available by default. No extra configuration is needed.
■ AWR file stats are the statistics generated by the database only. File stats from
Veritas File System include both database transaction and other IO like
backup/restore.
■ In a clustered Oracle RAC environment, AWR file stats include I/O from all
the nodes. There is no need to collect from each node and sum it up.
■ AWR file statistics provides history and hence it is easy to get the usage trends.
AWR also provides Oracle object level statistics like segment statistics. These can
be used to find out the least used table segments.
One large disadvantage of Oracle file statistics is that they do not provide statistics
at less than the file level.
Optimizing storage for Oracle database objects
To adopt a successful SmartTier policy and save storage costs, a method is needed
for relocating Oracle objects which are accessed infrequently to the secondary
tier. Relocating the entire file is not useful in all cases.
Only data segments are suitable for relocation, and they may be spread among
several datafiles. When new rows are inserted in a table, Oracle allocates space
for the table on demand. Oracle allocates space through one or more extents.
Because of this allocation scheme a given datafile will have:
■ Multiple extents belonging to more than one table.
■ The extents belonging to a table may not be contiguous in the file.
■ Each datafile will have a header and headers are updated at every database
checkpoint.
■ Relocating a file to a secondary storage tier means relocating rows/data
belonging to one or more tables.
■ If an entire datafile is relocated to a secondary storage tier, the Oracle
checkpoint performance may suffer and there will be some performance loss.
Oracle introduced locally managed tablespaces in Oracle 9i. When a tablespace
is locally managed:
■ The free space in a datafile is managed using a bitmap which is kept right next
to datafile header.
■ Each bit in the bitmap represents 1MB of storage in the file.
■ Free space management using bitmaps is far superior to dictionary managed
datafiles.
Understanding storage tiering with SmartTier
How SmartTier for Oracle works
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