Tuning Global Cache - Expert Oracle RAC Performance Diagnostics and Tuning - page 436

SCANMISSES NUMBER
SCANCOMPLETES NUMBER
MODIFICATIONS NUMBER
FLUSHES NUMBER
DLM_REQUESTS NUMBER
DLM_CONFLICTS NUMBER
DLM_RELEASES NUMBER
A common parameter that should be of concern in a RAC environment is the dc_sequences . This indicates that
there are not enough cache sizes defined for the various sequences used by the application. Tuning or increasing the
cache sizes for the commonly used database sequences should help reduce the contention.
Similar to the GV$LIBRARYCACHE view discussed earlier, Oracle maintains statistics from the DLM for the
parameters available in GV$ROWCACHE view. These columns give indications on global level requests, conflicts,
or contention and how frequently the objects managed by the parameter are released:
Script: MVRACPDnTap_rowcache.sql
SELECT inst_id INT,
parameter,
SUM(gets) gets,
SUM(getmisses) misses,
100 * SUM(gets - getmisses) / SUM(gets) pct_succ_gets,
SUM(modifications) updates
FROM gv$rowcache
WHERE gets > 0
GROUP BY inst_id,
parameter
ORDER BY inst_id;
INT PARAMETER GETS MISSES PCT_SUCC_GETS UPDATES
---- ----------------------- ----------- -------- ------------- --------
1 dc_awr_control 2419 133 94.5 14
dc_files 504 84 83.3 0
dc_global_oids 1671 37 97.8 0
dc_histogram_data 854110 6643 99.2 0
dc_histogram_defs 332053 12613 96.2 2,766
dc_object_grants 179 43 76.0 0
dc_objects 19529704 11766 99.9 6,174
dc_profiles 9304 2 100.0 0
dc_rollback_segments 1350573 2216 99.8 69
dc_segments 2526359 36460 98.6 1,275
dc_sequences 437 113 74.1 437
dc_table_scns 92 31 66.3 0
dc_tablespaces 2466261 30 100.0 0
dc_users 3546497 2098 99.9 0
global database name 119406 1 100.0 0
kqlsubheap_object 280915 89 100.0 0
outstanding_alerts 5345 4953 7.3 363
sch_lj_objs 4 4 .0 0
sch_lj_oids 197 14 92.9 0
History of this data is maintained in DBA_HIST_ROWCACHE_SUMMARY.