You should save this link in your bookmarks, for the next time you accidentally remove your database’s online redologs or overwrite some ASM disks:
Laurent Demaret has written a good article about how he systematically troubleshooted cache buffers chains latch contention, starting from wait interface and drilling down into details with my latchprofx tool:
Continuing with the post titled "Nested Loops and Consistent Gets" earlier today, what is the Execution Plan with statistics on more columns ?
SQL> exec dbms_stats.gather_table_stats('','TRANSACTIONS',estimate_percent=>100,granularity=>'ALL',-
> method_opt=>'FOR COLUMNS COUNTRY_CD SIZE 250, PRODUCT_CD SIZE 250, TXN_ID SIZE 250 ',cascade=>TRUE);
PL/SQL procedure successfully completed.
For my new book on Oracle indexing, I’d like to provide guidance on detecting when the block references in a secondary index on an index-organized table (IOT) need to be updated. All that I could find using my second brain were unsubstantiated claims that a secondary index should be rebuilt when PCT_DIRECT_ACCESS falls below 30. [...]
DBAs with a few years of experience and/or having read some material on performance tuning know that eliminating physical reads and achieving a high buffer cache hit ratio isn't necessarily a tuning goal.
Some DBAs have accepted the idea that, rather than physical reads, they should concentrate on logical reads -- consistent gets in case of queries.
But ...... there really is no "absolutely correct optimization target". Everything is relative.
When we have Exadata, we might ask some questions, what dynamic V$ views we can use for monitoring?
V$CELL - to display Exadata Cell Identification.
SQL> desc v$cell
Name Null? Type
----------------------------------------- -------- ----------------------------
CELL_PATH - IP addresses of the cell.
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