Expert Oracle Exadata - Parent Directory

CHAPTER 10 EXADATA WAIT EVENTSTABLE ACCESS STORAGE FULL 20TABLE ACCESS STORAGE SAMPLE 1As you can see, the vast majority of these events were motivated by index access paths. By the way,on non-Exadata platforms, noncontiguous multi-block reads still clock time to the old db file parallelread event. It’s also possible for this older wait event name to show up on an Exadata platform for someoperations.ParametersThe cell list of blocks physical read event provides more information than most cell events. Thefollowing parameters allow you to tell exactly which object was read along with identifying the disk andcell where the block was stored.P1 - Cell hash numberP2 - Disk hash numberP3 - Number of blocks readobj# - The object number of the object being readcell smart file creationExadata has an optimization technique that allows the storage cells to do the initialization of blockswhen a data file is created or extended. This occurs when a tablespace is created or a data file ismanually added to a tablespace. However, it can also occur when a data file is automatically extendedduring DML operations.Event MeaningWe previously stated that this event seemed out of place in the User I/O class. However, if it occursbecause of DML operations, it makes sense to have it in this category. At any rate, offloading the blockformatting eliminates CPU usage and I/O from the database servers and moves it to the storage tier.When this occurs, time is collected in the cell smart file creation event. This event replaces the Datafile init write event that is still used on non-Exadata platforms. Here is the output of a query from abusy production system showing operations that generated this event:SYS@EXDB1> select event, operation, count(*) from (2 select sql_id, event, sql_plan_operation||' '||sql_plan_options operation3 from DBA_HIST_ACTIVE_SESS_HISTORY4 where event like 'cell smart file%')5 group by operation, event6 order by 1,2,37 /EVENT OPERATION COUNT(*)-------------------------- ------------------------- --------cell smart file creation 35DELETE 3INDEX BUILD NON UNIQUE 5332