How to disable flush of ASH data to AWR?

MMON process will periodically flush ASH data into AWR tables.
Oracle introduced WF enqueue which is used to serialize the flushing of snapshots.

If for any reason ( space issue, bugs, hanging etc..) you need to disable flushing the run time statistics for
particular table than following procedure needs to be done.

First, locate the exact AWR Table Info (KEW layer):

SQL> select table_id_kewrtb, table_name_kewrtb from x$kewrtb order by 1

TABLE_ID_KEWRTB TABLE_NAME_KEWRTB
--------------- --------------------------------------------------------
0 WRM$_DATABASE_INSTANCE
1 WRM$_SNAPSHOT
2 WRM$_BASELINE
3 WRM$_WR_CONTROL
4 WRH$_STAT_NAME
5 WRH$_PARAMETER_NAME
6 WRH$_EVENT_NAME
7 WRH$_LATCH_NAME
8 WRH$_FILESTATXS
9 WRH$_TEMPSTATXS
10 WRH$_DATAFILE
11 WRH$_TEMPFILE
12 WRH$_SQLSTAT
13 WRH$_SQLTEXT
14 WRH$_SQL_SUMMARY
15 WRH$_SQL_PLAN
16 WRH$_SYSTEM_EVENT
17 WRH$_BG_EVENT_SUMMARY
18 WRH$_WAITSTAT
19 WRH$_ENQUEUE_STAT
20 WRH$_LATCH
21 WRH$_LATCH_CHILDREN
22 WRH$_LATCH_PARENT
23 WRH$_LATCH_MISSES_SUMMARY
24 WRH$_LIBRARYCACHE
25 WRH$_DB_CACHE_ADVICE
26 WRH$_BUFFER_POOL_STATISTICS
27 WRH$_ROWCACHE_SUMMARY
28 WRH$_SGA
29 WRH$_SGASTAT
30 WRH$_PGASTAT
31 WRH$_RESOURCE_LIMIT
32 WRH$_SHARED_POOL_ADVICE
33 WRH$_SQL_WORKAREA_HISTOGRAM
34 WRH$_PGA_TARGET_ADVICE
35 WRH$_INSTANCE_RECOVERY
36 WRH$_SYSSTAT
37 WRH$_PARAMETER
38 WRH$_UNDOSTAT
39 WRH$_PROCESS_MEMORY_SUMMARY
40 WRH$_SEG_STAT
41 WRH$_SEG_STAT_OBJ
42 WRH$_DLM_MISC
43 WRH$_SERVICE_NAME
44 WRH$_SERVICE_STAT
45 WRH$_ACTIVE_SESSION_HISTORY
46 WRH$_SYSMETRIC_HISTORY
47 WRH$_FILEMETRIC_HISTORY
48 WRH$_WAITCLASSMETRIC_HISTORY
49 WRI$_ALERT_HISTORY
50 WRH$_TABLESPACE_STAT
51 WRH$_LOG
52 WRH$_MTTR_TARGET_ADVICE
53 WRH$_TABLESPACE_SPACE_USAGE
54 WRH$_METRIC_NAME
55 WRH$_SYSMETRIC_SUMMARY
56 WRH$_SQL_BIND_METADATA
57 WRH$_JAVA_POOL_ADVICE
58 WRH$_THREAD
59 WRH$_SESSMETRIC_HISTORY
60 WRH$_OSSTAT
61 WRH$_OSSTAT_NAME
62 WRH$_SYS_TIME_MODEL
63 wri$_optstat_opr
64 WRH$_OPTIMIZER_ENV
65 WRM$_SNAP_ERROR
66 WRH$_SERVICE_WAIT_CLASS
67 WRH$_CR_BLOCK_SERVER
68 WRH$_CURRENT_BLOCK_SERVER
69 WRH$_INST_CACHE_TRANSFER
70 SQL Group
71 Segment Group
72 Datafile Group
73 Tempfile Group
74 Service Group
75 Undo Group
76 WRH$_STREAMS_POOL_ADVICE
77 WRI$_SEGADV_OBJLIST
78 WRI$_SEGADV_CNTRLTAB
79 WRH$_COMP_IOSTAT
80 WRH$_SGA_TARGET_ADVICE
81 WRH$_SESS_TIME_STATS
82 WRH$_STREAMS_CAPTURE
83 WRH$_STREAMS_APPLY_SUM
84 WRH$_BUFFERED_QUEUES
85 WRH$_BUFFERED_SUBSCRIBERS
86 WRH$_RULE_SET
87 WRH$_EVENT_HISTOGRAM
88 WRH$_MUTEX_SLEEP
89 WRH$_MEMORY_TARGET_ADVICE
90 WRH$_MEMORY_RESIZE_OPS
91 WRH$_PERSISTENT_QUEUES
92 WRH$_PERSISTENT_SUBSCRIBERS
93 WRM$_COLORED_SQL
94 WRH$_IOSTAT_FUNCTION
95 WRH$_IOSTAT_FUNCTION_NAME
96 WRH$_IOSTAT_FILETYPE
97 WRH$_IOSTAT_FILETYPE_NAME
98 WRH$_RSRC_CONSUMER_GROUP
99 WRH$_RSRC_PLAN
100 WRM$_BASELINE_DETAILS
101 WRM$_BASELINE_TEMPLATE
102 WRH$_CLUSTER_INTERCON
103 WRH$_MEM_DYNAMIC_COMP
104 WRH$_IC_CLIENT_STATS
105 WRH$_IC_DEVICE_STATS
106 WRH$_INTERCONNECT_PINGS
107 WRH$_DISPATCHER
108 WRH$_SHARED_SERVER_SUMMARY
109 WRH$_IOSTAT_DETAIL
110 WRH$_DYN_REMASTER_STATS
111 WRH$_PLAN_OPERATION_NAME
112 WRH$_PLAN_OPTION_NAME
113 WRH$_SQLCOMMAND_NAME
114 WRH$_TOPLEVELCALL_NAME
115 WRM$_WR_USAGE
116 WRH$_MVPARAMETER
117 WRH$_PERSISTENT_QMN_CACHE
118 WRH$_TABLESPACE
119 WRM$_SNAPSHOT_DETAILS
120 WRI$_SQLTEXT_REFCOUNT

121 rows selected.

1st option :

SQL> alter system set “_awr_disabled_flush_tables”=’<table_name>’;

e.g.

alter system set “_awr_disabled_flush_tables”=’WRH$_INTERCONNECT_PINGS,WRH$_RSRC_PLAN’;

System altered.

2nd option:

SQL> alter session set events ‘immediate trace name awr_flush_table_off level 106′;
SQL> alter session set events ‘immediate trace name awr_flush_table_off level 99′

If you decide to turn on flushing statistics than

SQL> alter session set events ‘immediate trace name awr_flush_table_on level 106′;
SQL> alter session set events ‘immediate trace name awr_flush_table_on level 99′;