Hidden Parameters in Oracle AI Database 26ai H.16 Undo / flashback (57)

 

Name	Type	Value	At default?	Level	PDB	RAC inst.	Flags	Description
_flashback_11_1_block_new_opt	Boolean	FALSE	yes	STATIC	N	N		use 11.1 flashback block new optimization scheme
_flashback_allow_noarchivelog	Boolean	FALSE	yes	SYSTEM imm.	N	Y		Allow enabling flashback on noarchivelog database
_flashback_archiver_partition_size	Integer	0	yes	SYSTEM imm.	N	Y		flashback archiver table partition size
_flashback_barrier_interval	Integer	1800	yes	STATIC	N	N		Flashback barrier interval in seconds
_flashback_copy_latches	Integer	10	yes	STATIC	N	N		Number of flashback copy latches
_flashback_database_test_only	Boolean	FALSE	yes	SESSION	N	N		Run Flashback Database in test mode
_flashback_delete_chunk_MB	Integer	128	yes	SYSTEM imm.	N	Y		Amount of flashback log (in MB) to delete in one attempt
_flashback_dynamic_enable	Boolean	TRUE	yes	STATIC	N	N		enable flashback enable code path
_flashback_dynamic_enable_failure	Integer	0	yes	SYSTEM imm.	N	Y		Simulate failures during dynamic enable
_flashback_enable_ra	Boolean	TRUE	yes	STATIC	N	N		Flashback enable read ahead
_flashback_format_chunk_mb	Integer	4	yes	SYSTEM imm.	N	Y		Chunk mega-bytes for formatting flashback logs using sync write
_flashback_format_chunk_mb_dwrite	Integer	16	yes	SYSTEM imm.	N	Y		Chunk mega-bytes for formatting flashback logs using delayed write
_flashback_fuzzy_barrier	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Use flashback fuzzy barrier
_flashback_generation_buffer_size	Big integer	16777216	yes	STATIC	N	N		flashback generation buffer size
_flashback_hint_barrier_percent	Integer	20	yes	STATIC	N	N		Flashback hint barrier percent
_flashback_log_io_error_behavior	Integer	0	yes	SYSTEM imm.	N	N		Specify Flashback log I/O error behavior
_flashback_log_min_size	Integer	100	yes	STATIC	N	N		Minimum flashback log size
_flashback_log_rac_balance_factor	Integer	10	yes	SYSTEM imm.	N	Y		flashback log rac balance factor
_flashback_log_size	Integer	1000	yes	STATIC	N	N		Flashback log size
_flashback_logfile_enqueue_timeout	Integer	600	yes	STATIC	N	N		flashback logfile enqueue timeout for opens
_flashback_marker_cache_enabled	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Enable flashback database marker cache
_flashback_marker_cache_size	Integer	328	yes	STATIC	N	N		Size of flashback database marker cache
_flashback_marker_for_every_grp	Boolean	FALSE	yes	STATIC	N	N		generate a new flashback marker for every GRP
_flashback_max_log_size	Big integer	0	yes	SYSTEM imm.	N	N		Maximum flashback log size in bytes (OS limit)
_flashback_max_n_log_per_thread	Integer	2048	yes	STATIC	N	N		Maximum number of flashback logs per flashback thread
_flashback_max_standby_sync_span	Integer	300	yes	SYSTEM imm.	N	Y		Maximum time span between standby recovery sync for flashback
_flashback_n_log_per_thread	Integer	128	yes	STATIC	N	N		Desired number of flashback logs per flashback thread
_flashback_pdb_thread_filter_disable	Boolean	FALSE	yes	STATIC	N	N		disable per PDB thread filter optimization
_flashback_prepare_log	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Prepare Flashback logs in the background
_flashback_reclaim_monitor_window	Integer	7	yes	SYSTEM imm.	N	Y		Proactive flashback logs reclaimation window
_flashback_reclaim_speed_up	Boolean	FALSE	yes	SYSTEM imm.	N	Y		Proactive flashback logs reclaimation speed up
_flashback_size_based_on_redo	Boolean	TRUE	yes	SYSTEM imm.	N	Y		Size new flashback logs based on average redo log size
_flashback_standby_barrier_interval	Integer	1	yes	STATIC	N	N		Flashback standby barrier interval in seconds
_flashback_standby_check_barrier_MIRA	Integer	20	yes	STATIC	N	N		Flashback standby check barrier generation in seconds
_flashback_standby_check_minpfh_MIRA	Integer	15	yes	STATIC	N	N		Flashback standby check minimum high fuzzy scn in seconds
_flashback_stby_support_mira	Boolean	TRUE	yes	STATIC	N	N		Flashback database on standby supports MIRA
_flashback_validate_controlfile	Boolean	FALSE	yes	SYSTEM imm.	N	Y		validate flashback pointers in controlfile for 11.2.0.2 database
_flashback_verbose_info	Boolean	FALSE	yes	SYSTEM imm.	N	Y		Print verbose information about flashback database
_flashback_write_max_loop_limit	Integer	10	yes	SYSTEM imm.	N	Y		Flashback writer loop limit before it returns
_rollback_segment_count	Integer	0	yes	SYSTEM imm.	Y	Y		number of undo segments
_rollback_segment_initial	Integer	1	yes	STATIC	Y	N		starting undo segment number
_rollback_stopat	Integer	0	yes	SYSTEM imm.	N	Y		stop at -position to step rollback
_smu_debug_mode	Big integer	0	yes	SYSTEM imm.	Y	Y		- set debug event for testing SMU operations
_smu_error_simulation_site	Integer	0	yes	SESSION	Y	N		site ID of error simulation in KTU code
_smu_error_simulation_type	Integer	0	yes	SESSION	Y	N		error type for error simulation in KTU code
_smu_timeouts	String		yes	SYSTEM imm.	Y	Y		comma-separated AND double-quoted list of AUM timeouts: mql, tur, sess_exprn, qry_exprn, slot_intvl
_undo_autotune	Boolean	TRUE	yes	SYSTEM imm.	Y	Y		enable auto tuning of undo_retention
_undo_block_compression	Boolean	TRUE	yes	SESSION	Y	Y		enable undo block compression
_undo_debug_mode	Integer	0	yes	SESSION	Y	Y		debug flag for undo related operations
_undo_debug_usage	Integer	0	yes	SYSTEM imm.	N	Y		invoke undo usage functions for testing
_undo_ofd_enabled	Boolean	TRUE	yes	SYSTEM imm.	Y	Y		enable ordered offline drop of undo segments for datafile shrink
_undo_ofd_excess	Integer	10	yes	SYSTEM imm.	Y	Y		percent of excess undo segments to offline or drop
_undo_ofd_reserve	Integer	30	yes	SYSTEM imm.	Y	Y		percent of excess undo segments to keep online
_undo_retention_time_limit	Integer	3600	yes	SYSTEM imm.	Y	Y		undo retention time limit in seconds
_undo_tbs_slave_percent	Integer	0	yes	SYSTEM imm.	N	Y		Percentage of redo slaves for undo tablespace
_undotbs_regular_tables	Boolean	FALSE	yes	SYSTEM imm.	N	Y		Create regular tables in undo tablespace
_undotbs_stepdown_pcent	Integer	75	yes	SYSTEM imm.	N	Y		Undo Tablespace small allocation step down percentage