Oracle Scratchpad

January 12, 2022

19c Trivia

Filed under: Oracle — Jonathan Lewis @ 11:06 am GMT Jan 12,2022

Here’s a little detail I’ve just noticed in There are a lot of parameters with names like “\_bug%”, some having proper descriptions, some simply echoing their previous pattern of things like: “tenth spare parameter – integer”.

Parameter                                                 System Value         Description
--------------------------------------------------------- -------------------- ----------------------------------------------------------------------
_bug27355984_xt_preproc_timeout                           100                  external table preprocessor timeout
_bug28322973_asm_ownerid_trace_timeout                    600                  ownerid tracing threshold in seconds
_bug28482048_fb_log_max_rereads                           100                  Maximum number of rereads after reading a corrupt flashback block
_bug29274428_modsvc_call_out_enabled                      FALSE                one-hundred-and-forty-third spare parameter - boolean
_bug29290173_securefiles_dealloc_cfs                      0                    securefiles deallocate directly to CFS
_bug29302220_tcpinfo_statistics_save_atexit               FALSE                TCP Info Statistics Save At Exit
_bug29386835_enable_per_container_acl                     FALSE                Enable Per Container ACL
_bug29394014_allow_triggers_on_vpd_table                  FALSE                Allow triggers on VPD protected table in DM
_bug29504103_runtime_index_key_length_check               0                    allow runtime checking of index key length
_bug29558926_ctas_numfrags_hint                           0                    Hint for number of partition fragments to be loaded in a CTAS
_bug29796916_audit_sys_privilege                          TRUE                 one-hundred-and-seventy-ninth spare parameter - boolean
_bug29825525_bct_public_dba_buffer_dynresize_delay        3600                 sixth spare parameter - integer
_bug29903454_ksws_enable_alb                              TRUE                 enable ALB metrics processing
_bug30159581_cputime_limit_parallel_fptr                                       twenty-seventh spare parameter - integer
_bug30159581_runtime_limit_parallel_fptr                                       twenty-eighth spare parameter - integer
_bug30165506_unified_pga_max_pool_size                                         twenty-first spare parameter - integer
_bug30186319_lm_hb_lgio_timeout                           70                   LGWR io timeout in seconds
_bug30196629_dbopen_breakpoint                            none                 ALTER DATABASE OPEN codepath breakpoint
_bug30224950_kjac_direct_path_enabled                     TRUE                 one-hundred-and-fifty-fifth spare parameter - boolean
_bug30316897_allow_fallback_to_dbkey                      FALSE                one-hundred-and-sixty-third spare parameter - boolean
_bug30346330_hang_sess_enq_wait_blocked_session_threshold 5                    tenth spare parameter - integer
_bug30346330_hang_sess_enq_wait_resltn_trig_time          0                    seventeenth spare parameter - integer
_bug30352623_asm_enable_vfreloc_on_rm                     0                    Enable voting file relocation on rolling migration
_bug30382982_keep_relocated_source_pdb                    FALSE                one-hundred-and-sixty-second spare parameter - boolean
_bug30570083_mv_master_lock_timeout                       3                    timeout that mv create/drop waits to lock the master table
_bug30624792_hang_px_resolution_on_asm_enabled            TRUE                 Hang Management px resolution on ASM enabled
_bug31261467_disable_block_corruption_track               FALSE                one-hundred-and-seventy-eighth spare parameter - boolean
_bug31304945_utlfile_dirpath                              FALSE                return Utl_File Accessible
_bug31417007_lm_mp_additional_reg_buffers                 20                   forty-seventh spare parameter - integer
_bug31417007_lm_mp_share_lms_pools                        TRUE                 one-hundred-and-eighty-sixth spare parameter - boolean
_bug31417007_lm_mp_small_lms_pools                        TRUE                 one-hundred-and-eighty-seventh spare parameter - boolean
_bug31701239_hang_high_session_count_update_hb_threshold                       Hang Manager high session count update heartbeat threshold
_bug31720839_lm_ges_rht_alloc_size                        4096                 ges rht allocation chunk size
_bug31720839_lm_recovery_pdbw_reduction                   4                    recovery member pdbw reduction
_bug31734583_hang_analyze_elapsed_time_limit              1800                 Hang Analyze elapsed time limit in seconds
_bug31747989_cputime_limit_parallel_fptr                  60                   CPU-time limit for for parallel first-pass recovery
_bug31747989_runtime_limit_parallel_fptr                  60                   run-time limit for for parallel first-pass recovery
_bug31823051_asm_slow_client_timeout_percentage           50                   Percentage of the write cancel timeout to detect slow client.
_bug32093558_j0_deq_maxwait_time                          0                    forty-first spare parameter - integer
_bug32093558_srvntfn_max_job_time                         180                  fortieth spare parameter - integer
_bug32095097_defer_rcv_pdb_attach                         TRUE                 Defer PDB domain attach in instance recovery
_bug32171622_asm_reloc_restart_timeout                    900                  csecs before signaling ORA-15424 when waiting for orphans

42 rows selected.

It looks as if Oracle may be implementing a new strategy to replace the prevalence of fix_control settings to allow for improved visibility of the state of point patches. Possibly the aim is to cater for systems that have had to tweak multiple fix controls and have problems with the maximum length of the parameter value.

It’s interesting to note that has only 11 such parameters – some new and a few matching thise in I haven’t checked yet whether all the parameters that have disappeared from are still in 21.3.0. with the bug number prefix removed, but I’ve spotted a couple with that appearance.

Many years ago Coskan Gundogar wrote a note about checking v$system_fix_control to see if it gave any clues about unexpected (optimizer) behaviour: the method is still appropriate, but now you have another place to check.

Although one of these parameters is now the record holder for “longest parameter name”, the longest description belongs to a hidden parameter that isn’t a “bug” parameter.


The script to generate this list is available in this note about trace files, with most of the columns commented out. I’ve run the script from SQL*Plus using the command

start params "\_bug"

1 Comment »

  1. […] are a lot of “_bug%” parameters in the latest updates of 19c (the first one appeared in, possibly taking over […]

    Pingback by 12c trivia | Oracle Scratchpad — January 12, 2022 @ 11:10 am GMT Jan 12,2022 | Reply

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