Notice the inclusion of the online option in the alter index . . . rebuild statement. The
indexed table can remain online with minimal overhead while the index is rebuilding. In rare
circumstances, such as on longer key lengths, you may not be able to use the online option.
Space Usage Warning Levels
Earlier in this chapter, we reviewed the data dictionary view DBA_THRESHOLDS, which contains
a list of the active metrics to measure a database??™s health. In a default installation of Oracle 11g,
use the following select statement to see some of the 22 built-in thresholds:
SQL> select metrics_name, warning_operator warn, warning_value wval,
2 critical_operator crit, critical_value cval,
3 consecutive_occurrences consec
4 from dba_thresholds;
Chapter 6: Monitoring Space Usage 191
METRICS_NAME WARN WVAL CRIT CVAL CONSEC
-------------------------------- ---- ------------- ---- ------------- ------
Average Users Waiting Counts GT 10 NONE 3
. . .
Blocked User Session Count GT 0 NONE 15
Current Open Cursors Count GT 1200 NONE 3
Database Time Spent Waiting (%) GT 30 NONE 3
. . .
Logons Per Sec GE 100 NONE 2
Session Limit % GT 90 GT 97 3
Tablespace Bytes Space Usage LE 0 LE 0 1
Tablespace Space Usage GE 85 GE 97 1
22 rows selected.
In terms of space usage, we see that the warning level for a given tablespace is when the
tablespace is 85 percent full, and the space is at a critical level when it reaches 97 percent full.
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