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Oracle Tips by Burleson |
Secret Locking Parameters
This class of parameters allows the DBA to
start a Oracle database even though a data file is corrupt. The most
important of these parameters are:
* _allow_read_only_corruption – This
parameter is used by Oracle technical support when a database is
corrupt and the instance will not open. Setting this parameter
to TRUE allows a corrupt Oracle database to open so you can salvage
data manually.
* _allow_resetlogs_corruption – This is
a very useful tool for starting your Oracle database when Oracle
detects redo log corruption.
Secret Bypass Parms
List of undocumented Oracle parameters
Parameter
Current Instance
Name
Value Value
---------------------------------------- ----------
--------------------
Parameter
Description
------------------------------------------------------------------------------
_allow_error_simulation
FALSE FALSE
Allow error simulation for testing
_allow_read_only_corruption
FALSE FALSE
allow read-only open even if database is corrupt
_allow_resetlogs_corruption
FALSE FALSE
allow resetlogs even if it will cause corruption
_enable_NUMA_optimization
TRUE TRUE
Enable NUMA specific optimizations
_enable_block_level_transaction_recovery
TRUE TRUE
enable block level recovery
_enable_cscn_caching
TRUE TRUE
enable commit SCN caching for all transactions
_enable_default_affinity
0 0
to enable default implementation of affinity osds
_enable_kgh_policy
FALSE FALSE
temporary to disable/enable kgh policy
_enable_list_io
FALSE FALSE
Enable List I/O
_enable_multitable_sampling
FALSE FALSE
enable multitable sampling
_enable_type_dep_selectivity
TRUE TRUE
enable type dependent selectivity estimates
11 rows
selected.
Parallel parameters
Oracle provides a wealth of internal
parameters to control the behavior of parallel query, parallel DML and
Real Application Clusters (RAC).
* _parallelism_cost_fudge_factor – This
parameter controls the friendliness of parallel full-table scans.
* _parallel_default_max_instances - This
parameter sets the default maximum number of instances for parallel
query.
Parallel Processing
List of undocumented Oracle parameters
Parameter
Current Instance
Name
Value Value
---------------------------------------- ----------
--------------------
Parameter
Description
------------------------------------------------------------------------------_optimizer_percent_parallel
101 101
optimizer percent parallel
_parallel_adaptive_max_users
1 1
maximum number of users running with default DOP
_parallel_default_max_instances
1 1
default maximum number of instances for parallel query
_parallel_execution_message_align
FALSE FALSE
Alignment of PX buffers to OS page boundary
_parallel_fake_class_pct
0 0
fake db-scheduler percent used for testing
_parallel_load_bal_unit
0 0
number of threads to allocate per instance
_parallel_load_balancing
TRUE TRUE
parallel execution load balanced slave allocation
_parallel_min_message_pool
64440 64440
minimum size of shared pool memory to reserve for pq servers
_parallel_recovery_stopat
32767 32767
stop at -position- to step through SMON
_parallel_server_idle_time
5 5
idle time before parallel query server dies
_parallel_server_sleep_time
10 10
sleep time between dequeue timeouts (in 1/100ths)
_parallel_txn_global
FALSE FALSE
enable parallel_txn hint with updates and deletes
_parallelism_cost_fudge_factor
350 350
set the parallelism cost fudge factor
13 rows
selected.
For more details, see the "Easy
Oracle Series" a set of books especially designed by Oracle
experts to get you started fast with Oracle database technology.
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