Hidden Parameters in Oracle AI Database 26ai H.7 Memory / buffer cache (183)

 

Name	Type	Value	At default?	Level	PDB	RAC inst.	Flags	Description
_buffer_busy_wait_timeout	Integer	100	yes	SESSION	Y	Y		buffer busy wait time in centiseconds
_buffer_requests_to_drain	Integer	5	yes	SYSTEM imm.	Y	Y		Buffer for requests to drain before planned failover
_buffered_message_spill_age	Integer	300	yes	SYSTEM imm.	N	Y		Buffered message spill age
_buffered_publisher_flow_control_threshold	Integer	0	yes	SYSTEM imm.	N	Y		Flow control threshold for buffered publishers except capture
_db_block_adjcheck	Boolean	TRUE	yes	SYSTEM imm.	N	Y		adjacent cache buffer checks - low blkchk overwrite parameter
_db_block_adjchk_level	Integer	0	yes	SYSTEM imm.	N	Y		adjacent cache buffer check level
_db_block_align_direct_read	Boolean	TRUE	yes	STATIC	N	N		Align Direct Reads
_db_block_bad_write_check	Boolean	FALSE	yes	STATIC	N	N		enable bad write checks
_db_block_buffers	Big integer	288000	yes	STATIC	N	N		Number of database blocks cached in memory: hidden parameter
_db_block_cache_history_lru	Boolean	FALSE	yes	STATIC	N	N		buffer header tracing for lru operations
_db_block_cache_protect	String	false	yes	STATIC	N	N		protect database blocks (for debugging only)
_db_block_cache_protect_internal	Integer	0	yes	STATIC	N	N		protect database blocks (for internal use only)
_db_block_check_for_debug	Boolean	FALSE	yes	SYSTEM imm.	N	Y		Check more and dump block before image for debugging
_db_block_check_objtyp	Boolean	TRUE	yes	SYSTEM imm.	N	Y		check objd and typ on cache disk read
_db_block_chunkify_ncmbr	Boolean	FALSE	yes	SESSION	Y	Y		chunkify noncontig multi block reads
_db_block_corruption_recovery_threshold	Integer	30	yes	SYSTEM imm.	N	Y		threshold number of block recovery attempts
_db_block_do_full_mbreads	Boolean	FALSE	yes	SYSTEM imm.	N	Y		do full block read even if some blocks are in cache
_db_block_hash_buckets	Big integer	1048576	yes	STATIC	N	N		Number of database block hash buckets
_db_block_hash_latches	Integer	8192	yes	STATIC	N	N		Number of database block hash latches
_db_block_header_guard_level	Integer	0	yes	STATIC	N	N		number of extra buffer headers to use as guard pages
_db_block_hi_priority_batch_size	Integer	0	yes	STATIC	N	N		Fraction of writes for high priority reasons
_db_block_iterations_for_rm	Integer	2000	yes	SYSTEM imm.	N	Y		number of blocks to reduce every iteration for RM
_db_block_known_clean_pct	Integer	2	yes	STATIC	N	N		Initial Percentage of buffers to maintain known clean
_db_block_lru_latches	Integer	36	yes	STATIC	N	N		number of lru latches
_db_block_max_cr_dba	Integer	6	yes	STATIC	N	N		Maximum Allowed Number of CR buffers per dba
_db_block_max_scan_pct	Integer	40	yes	STATIC	N	N		Percentage of buffers to inspect when looking for free
_db_block_med_priority_batch_size	Integer	0	yes	STATIC	N	N		Fraction of writes for medium priority reasons
_db_block_numa	Integer	1	yes	STATIC	N	N		Number of NUMA nodes
_db_block_prefetch_fast_longjumps_enabled	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Batched IO enable fast longjumps
_db_block_prefetch_limit	Integer	0	yes	SYSTEM imm.	N	Y		Prefetch limit in blocks
_db_block_prefetch_override	Integer	0	yes	SYSTEM imm.	N	Y		Prefetch force override in blocks
_db_block_prefetch_private_cache_enabled	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Batched IO enable private cache
_db_block_prefetch_quota	Integer	10	yes	SYSTEM imm.	N	Y		Prefetch quota as a percent of cache size
_db_block_prefetch_skip_reading_enabled	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Batched IO enable skip reading buffers
_db_block_prefetch_wasted_threshold_perc	Integer	2	yes	SYSTEM imm.	N	Y		Allowed wasted percent threshold of prefetched size
_db_block_scandepth_for_rm	Integer	20	yes	SYSTEM imm.	N	Y		number of blocks to reduce every iteration for RM
_db_block_table_scan_buffer_size	Big integer	4194304	yes	STATIC	N	N		Size of shared table scan read buffer
_db_block_temp_redo	Boolean	FALSE	yes	SYSTEM imm.	N	Y		generate redo for temp blocks
_db_block_trace_protect	Boolean	FALSE	yes	SYSTEM imm.	N	Y		trace buffer protect calls
_db_block_vlm_check	Boolean	FALSE	yes	STATIC	N	N		check for mapping leaks (debugging only)
_db_block_vlm_leak_threshold	Integer	4	yes	STATIC	N	N		threshold for allowable mapping leaks
_db_blocks_per_hash_latch	Integer		yes	STATIC	N	N		Number of blocks per hash latch
_db_cache_advice_hash_latch_multiple	Integer	16	yes	STATIC	N	N		cache advisory hash latch multiple
_db_cache_advice_max_size_factor	Integer	2	yes	STATIC	N	N		cache advisory maximum multiple of current size to similate
_db_cache_advice_sample_factor	Integer	4	yes	STATIC	N	N		cache advisory sampling factor
_db_cache_advice_sanity_check	Boolean	FALSE	yes	STATIC	N	N		cache simulation sanity check
_db_cache_advice_size_submultiple	Integer	10	yes	STATIC	N	N		cache advisory size submultiple
_db_cache_block_read_stack_trace	Integer	0	yes	SYSTEM imm.	Y	Y		dump short call stack for block reads
_db_cache_block_read_stack_trace_where1	Integer	0	yes	SYSTEM imm.	Y	Y		dump short call stack for block reads just for where1
_db_cache_block_read_stack_trace_where2	Integer	0	yes	SYSTEM imm.	Y	Y		dump short call stack for block reads just for where2
_db_cache_block_read_stack_trace_where3	Integer	0	yes	SYSTEM imm.	Y	Y		dump short call stack for block reads just for where3
_db_cache_crx_check	Boolean	FALSE	yes	STATIC	N	N		check for costly crx examination functions
_db_cache_max_sz	Big integer	0	yes	SYSTEM imm.	Y	Y
_db_cache_min_sga_perc	Integer	0	yes	SYSTEM imm.	N	Y		Make db_cache_size min this percentage of sga_target
_db_cache_miss_check_les	Boolean	FALSE	yes	SESSION	Y	Y		check LEs after cache miss
_db_cache_mman_latch_check	Boolean	FALSE	yes	STATIC	N	N		check for wait latch get under MMAN ops in kcb
_db_cache_numa_tol_enable	Integer	10	yes	SYSTEM imm.	N	Y		Enable/disable numa imbalance in cache granules
_db_cache_numa_tolerance	Integer	5	yes	SYSTEM imm.	N	Y		Allow this much numa imbalance in cache granules
_db_cache_pmem_confidence_try	Integer	0	yes	SYSTEM imm.	N	Y		DB Cache PMEM buffer promote attempts for greater confidence
_db_cache_pmem_promotion_touch_rate_reset_interval	Integer	300	yes	SYSTEM imm.	N	Y		DB Cache PMEM promotion touch rate reset interval in sec
_db_cache_pmem_promotion_touch_rate_threshold_time	Integer	30	yes	SYSTEM imm.	N	Y		DB Cache PMEM promotion touch rate threshold time in sec
_db_cache_pmem_touch_rate_compare_per	Integer	95	yes	SYSTEM imm.	N	Y		DB Cache PMEM buffer touch rate additive percentage when comparingagainst dram touch rate
_db_cache_pmemp_len	Integer	10000	yes	SYSTEM imm.	N	Y		DB Cache PMEM promotion list max length
_db_cache_pre_warm	Boolean	TRUE	yes	STATIC	N	N		Buffer Cache Pre-Warm Enabled : hidden parameter
_db_cache_process_cr_pin_max	Integer	2147483647	yes	SYSTEM imm.	N	Y		maximum number of cr pins a process may have
_db_cache_read_temp_as_cur_on_standby	Boolean	TRUE	yes	SESSION	Y	Y		if TRUE, read temp space blocks as current on standby
_db_cache_silicon_secured_memory	Boolean	TRUE	yes	STATIC	N	N		enable silicon secured memory
_db_cache_wait_debug	Integer	0	yes	SYSTEM imm.	N	Y		trace new kslwaits
_db_cache_xmem_promotion_algo_chosen	Integer	38	yes	SYSTEM imm.	N	Y		DB Cache Xmem/Pmem promotion algo
_db_cache_xmem_size	Big integer	0	yes	SYSTEM imm.	N	Y		Size of extended memory data area for buffer cache DEFAULT pool
_kgh_free_list_min_effort	Integer	12	yes	SYSTEM imm.	N	Y		typical number of free list chunks to visit
_kgh_restricted_subheaps	Integer	180	yes	SYSTEM imm.	N	Y		number of subheaps in heap restricted mode
_kgh_restricted_trace	Integer	0	yes	SYSTEM imm.	N	Y		trace level for heap dump-restricted mode
_kghdsidx_count	Integer	1	yes	STATIC	N	N		max kghdsidx count
_kghdsidx_lp_count	Integer	1	yes	STATIC	N	N		number of child latches for large pool and shared with Java pool
_kghdsidx_numa_count	Integer	1	yes	STATIC	N	N		number of child latches for NUMA pools
_kghdsidx_sp_count	Integer	1	yes	STATIC	N	N		number of child latches for shared pool and shared with Java pool
_kghdsidx_streams_count	Integer	1	yes	STATIC	N	N		number of child latches for Streams pool
_kgl_4021_assert_on_oso	Boolean	FALSE	yes	SESSION	Y	Y		Raise soft assert on hitting ORA-4021 for Oracle supplied object
_kgl_assert_x_pin	Boolean	FALSE	yes	SYSTEM imm.	Y	Y		assert if KGL takes an X-pin on PL/SQL
_kgl_automatic_retry_on_deadlock	Boolean	TRUE	yes	SESSION	Y	Y		disable automatic deadlock retry
_kgl_bucket_bitvector	Boolean	TRUE	yes	STATIC	N	N		Enable creation of PDB bit vector in KGL Hash Buckets
_kgl_bucket_bitvector_clear	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Enable clearing library cache bucket bit vector
_kgl_bucket_count	Integer	9	yes	STATIC	N	N		Library cache hash table bucket count (2^_kgl_bucket_count * 256)
_kgl_bypass_options_load	Integer	0	yes	SESSION	Y	Y		disable loading of options for exceptional situations
_kgl_cluster_lock	Boolean	TRUE	yes	STATIC	Y	N		Library cache support for cluster lock
_kgl_cluster_lock_read_mostly	Boolean	FALSE	yes	STATIC	N	N		Library cache support for cluster lock read mostly optimization
_kgl_cluster_pin	Boolean	TRUE	yes	STATIC	Y	N		Library cache support for cluster pins
_kgl_debug	String		yes	SESSION	Y	Y		Library cache debugging
_kgl_final_blocker_kill_begin_time	Integer	2	yes	SESSION	Y	Y		time to wait in minutes before start killing blockers
_kgl_fixed_extents	Boolean	TRUE	yes	STATIC	N	N		fixed extent size for library cache memory allocations
_kgl_hash_collision	Boolean	FALSE	yes	STATIC	Y	N		Library cache name hash collision possible
_kgl_heap_size	Integer	4096	yes	STATIC	N	N		extent size for library cache heap 0
_kgl_hot_object_copies	Integer	0	yes	STATIC	Y	N		Number of copies for the hot object
_kgl_iterator_action	String	SKIP	yes	SESSION	Y	Y		Action to take if we dereference in-flux state in kgl iterator
_kgl_kill_final_blocker	Boolean	FALSE	yes	SESSION	Y	Y		controls feature to kill KGL X lock/pin blockers
_kgl_kqr_cap_so_stacks	Integer	0	yes	SESSION	Y	Y		capture stacks for library and row cache state objects
_kgl_large_heap_assert_threshold	Integer	1500000000	yes	SYSTEM imm.	Y	Y		maximum heap size before KGL raises an internal error
_kgl_large_heap_warning_threshold	Integer	52428800	yes	SYSTEM imm.	Y	Y		maximum heap size before KGL writes warnings to the alert log
_kgl_latch_count	Integer	0	yes	STATIC	N	N		number of library cache latches
_kgl_max_wait_time_during_kill	Integer	15	yes	SESSION	Y	Y		max time to wait to get unblocked while killing blockers
_kgl_min_cached_so_count	Integer	1	yes	SESSION	Y	Y		Minimum cached SO count. If > 1 can help find SO corruptions
_kgl_skip_octcode_dlk_retry	Big integer	65535	yes	SESSION	Y	Y		OCTCODEs to skip for deadlock retry
_kgl_time_to_wait_for_locks	Integer	15	yes	SESSION	Y	Y		time to wait for locks and pins before timing out
_kglpgmtx_cap_uol_stack	Boolean	FALSE	yes	SESSION	Y	Y		Capture short stack upon mutex get
_kglsim_maxmem_percent	Integer	5	yes	STATIC	N	N		max percentage of shared pool size to be used for KGL advice
_large_pool_min_alloc	Big integer	65536	yes	STATIC	N	N		minimum allocation size in bytes for the large allocation pool
_mem_annotation_pr_lev	Integer	0	yes	STATIC	N	N		private memory annotation collection level
_mem_annotation_scale	Integer	1	yes	STATIC	N	N		memory annotation pre-allocation scaling
_mem_annotation_sh_lev	Integer	0	yes	STATIC	N	N		shared memory annotation collection level
_mem_annotation_store	Boolean	FALSE	yes	STATIC	N	N		memory annotation in-memory store
_mem_std_extent_size	Integer	4096	yes	STATIC	N	N		standard extent size for fixed-size-extent heaps
_memory_adi_bytes_per_alloc	Integer	0	yes	STATIC	N	N		bytes per allocation to get memory application data integrity
_memory_adi_clear_versions	Boolean	FALSE	yes	STATIC	N	N		enable clearing versions on huge pages
_memory_adi_enabled	Boolean	FALSE	yes	STATIC	N	N		enable memory application data integrity
_memory_adi_extend	Boolean	FALSE	yes	STATIC	N	N		enable ADI for kgh headers and free memory
_memory_adi_heap_mask	Integer	610	yes	STATIC	N	N		enable ADI versioning for these heaps
_memory_adi_module_mask	Integer	0	yes	STATIC	N	N		bit mask of modules to enable ADI versioning
_memory_adi_precise_errors	Boolean	FALSE	yes	STATIC	N	N		enable precise memory application data integrity errors
_memory_broker_log_stat_entries	Integer	5	yes	STATIC	N	N		memory broker num stat entries
_memory_broker_marginal_utility_bc	Integer	12	yes	SYSTEM imm.	N	Y		Marginal Utility threshold pct for bc
_memory_broker_marginal_utility_imc	Integer	6	yes	SYSTEM imm.	N	Y		Marginal Utility threshold pct for imc
_memory_broker_marginal_utility_sp	Integer	7	yes	SYSTEM imm.	N	Y		Marginal Utility threshold pct for sp
_memory_broker_sga_grow_split	Boolean	TRUE	yes	SYSTEM imm.	N	Y		if TRUE, allow sga grow to be split between cache and sp
_memory_broker_sga_grow_splitif_size	Integer	20	yes	SYSTEM imm.	N	Y		split sga target grow if atleast this many granules.
_memory_broker_sga_shrink_chunk_size	Integer	20	yes	SYSTEM imm.	N	Y		if kmgsbshnkbrk set, sga request resize chunk size in granules.
_memory_broker_sga_shrink_chunked	Boolean	TRUE	yes	SYSTEM imm.	N	Y		if TRUE, break a large sga shrink request to chunks
_memory_broker_shrink_heaps	Integer	15	yes	SYSTEM imm.	N	Y		memory broker allow policy to shrink shared pool
_memory_broker_shrink_imc	Integer	15	yes	SYSTEM imm.	N	Y		memory broker allow policy to shrink imc pool
_memory_broker_shrink_java_heaps	Integer	900	yes	SYSTEM imm.	N	Y		memory broker allow policy to shrink java pool
_memory_broker_shrink_streams_pool	Integer	900	yes	SYSTEM imm.	N	Y		memory broker allow policy to shrink streams pool
_memory_broker_shrink_timeout	Big integer	60000000	yes	SYSTEM imm.	N	Y		memory broker policy to timeout shrink shared/java pool
_memory_broker_stat_interval	Integer	30	yes	SYSTEM imm.	N	Y		memory broker statistics gathering interval for auto sga
_memory_checkinuse_timeintv	Integer	30	yes	SYSTEM imm.	N	Y		check inuse time interval
_memory_imm_mode_without_autosga	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Allow immediate mode without sga/memory target
_memory_initial_sga_split_perc	Integer	60	yes	STATIC	N	N		Initial default sga target percentage with memory target
_memory_management_tracing	Integer	0	yes	SYSTEM imm.	N	Y		trace memory management activity
_memory_max_tgt_inc_cnt	Integer	0	yes	SYSTEM imm.	N	Y		counts the times checker increments memory target
_memory_mgmt_fail_immreq	Boolean	FALSE	yes	SYSTEM imm.	N	Y		always fail immediate mode request
_memory_mgmt_immreq_timeout	Integer	150	yes	SYSTEM imm.	N	Y		time in seconds to time out immediate mode request
_memory_nocancel_defsgareq	Boolean	FALSE	yes	SYSTEM imm.	N	Y		do not cancel deferred sga reqs with auto-memory
_memory_per_cpu_count	Big integer	0	yes	STATIC	N	N		memory per cpu count
_memory_sanity_check	Integer	0	yes	SYSTEM imm.	N	Y		partial granule sanity check
_pga_aggregate_xmem_limit	Big integer	0	yes	SYSTEM imm.	N	Y		limit of aggregate PGA XMEM memory consumed by the instance
_pga_auto_snapshot_percentage	Integer	20	yes	SYSTEM imm.	N	Y		percent growth of PGA memory for additional snapshots
_pga_auto_snapshot_threshold	Big integer	524288000	yes	SYSTEM imm.	N	Y		bytes of PGA memory in one process to trigger detail snapshot
_pga_in_sga_param1	String		yes	SYSTEM imm.	N	Y		pga in sga param1
_pga_in_sga_param2	String		yes	SYSTEM imm.	Y	Y		pga in sga param2
_pga_in_sga_param3	String		yes	SYSTEM imm.	Y	Y		pga in sga param4
_pga_in_sga_param4	Integer		yes	SYSTEM imm.	Y	Y		pga in sga param4
_pga_in_sga_param5	Integer		yes	SYSTEM imm.	Y	Y		pga in sga param4
_pga_incident_app_usage_perc	Integer	75	yes	SYSTEM imm.	N	Y		suppress PGA limit incidents if app use above this percent
_pga_large_extent_size	Big integer	1048576	yes	STATIC	N	N		PGA large extent size
_pga_limit_check_wait_time	Integer	1000000	yes	SYSTEM imm.	N	Y		microseconds to wait for over limit confirmation
_pga_limit_dump_summary	Boolean	TRUE	yes	SYSTEM imm.	N	Y		dump PGA summary when signalling ORA-4036
_pga_limit_interrupt_smaller	Boolean	FALSE	yes	SYSTEM imm.	N	Y		whether to interrupt smaller eligible processes
_pga_limit_min_req_size	Big integer	4194304	yes	SYSTEM imm.	N	Y		bytes of PGA usage below which process will not get ORA-4036
_pga_limit_per_process_minimum	Big integer	3145728	yes	SYSTEM imm.	N	Y		pga_aggregate_limit per-process minimum
_pga_limit_physmem_perc	Integer	90	yes	SYSTEM imm.	N	Y		default percent of physical memory for pga_aggregate_limit and SGA
_pga_limit_simulated_physmem_size	Big integer	0	yes	SYSTEM imm.	N	Y		bytes of physical memory to determine pga_aggregate_limit with
_pga_limit_target_perc	Integer	200	yes	SYSTEM imm.	N	Y		default percent of pga_aggregate_target for pga_aggregate_limit
_pga_limit_time_to_interrupt	Integer	2	yes	SYSTEM imm.	N	Y		seconds to wait until direct interrupt
_pga_limit_time_until_idle	Integer	15	yes	SYSTEM imm.	N	Y		seconds to wait before treating process as idle
_pga_limit_time_until_killed	Integer	30	yes	SYSTEM imm.	N	Y		seconds to wait before killing session over limit
_pga_limit_tracing	Integer	0	yes	SYSTEM imm.	N	Y		trace pga_aggregate_limit activity
_pga_limit_use_immediate_kill	Boolean	TRUE	yes	SYSTEM imm.	N	Y		use immediate kill for sessions over limit
_pga_limit_watch_perc	Integer	50	yes	SYSTEM imm.	N	Y		percentage of limit to have processes watch
_pga_limit_watch_size	Big integer	104857600	yes	SYSTEM imm.	N	Y		bytes of PGA usage at which process will begin watching limit
_pga_max_size	Big integer	209715200	yes	SYSTEM imm.	N	Y		Maximum size of the PGA memory for one process
_pgactx_cap_stacks	Boolean	FALSE	yes	SESSION	Y	Y		capture stacks for setting pgactx
_sga_alloc_slaves_term_timeout_secs	Integer	120	yes	STATIC	N	N		Termination timeout in secs for SA** slaves
_sga_clear_dump	Boolean	FALSE	yes	SESSION	Y	Y		Allow dumping encrypted blocks in clear for debugging
_sga_early_trace	Integer	0	yes	SYSTEM imm.	N	Y		sga early trace event
_sga_grow_batch_size	Big integer	2147483648	yes	STATIC	N	N		Dynamic SGA grow batch size
_sga_heap_chunk_alignment	Boolean	FALSE	yes	STATIC	N	N		force SGA heap chunk alignment
_sga_heap_chunk_alignment_disabled	Boolean	FALSE	yes	STATIC	N	N		force SGA heap chunks not to be aligned
_sga_shrink_allow	Boolean	FALSE	yes	STATIC	N	N		Allow SGA shrink operation
_shared_pool_lru_bufs	Integer	200	yes	SYSTEM imm.	N	Y		shared pool lru effort buffer size
_shared_pool_max_size	Big integer	0	yes	SYSTEM imm.	N	Y		shared pool maximum size when auto SGA enabled
_shared_pool_max_sz	Big integer	0	yes	SYSTEM imm.	Y	Y
_shared_pool_minsize_on	Boolean	FALSE	yes	SYSTEM imm.	N	Y		shared pool minimum size when auto SGA enabled
_shared_pool_reserved_min_alloc	Big integer	4400	yes	STATIC	N	N		minimum allocation size in bytes for reserved area of shared pool
_shared_pool_reserved_pct	Integer	7	yes	STATIC	N	N		percentage memory of the shared pool allocated for the reserved area