Oracle ASM hidden parameters

_lm_asm_enq_hashing
_ges_diagnostics_asm_dump_level
_asm_runtime_capability_volume_support
_asm_disable_multiple_instance_check
_asm_disable_amdu_dump
_asmsid
_asm_allow_system_alias_rename
_asm_instlock_quota
asm_diskstring
_asm_disk_repair_time
asm_preferred_read_failure_groups
_asm_disable_profilediscovery
_asm_imbalance_tolerance
_asm_shadow_cycle
_asm_primary_load_cycles
_asm_primary_load
_asm_secondary_load_cycles
_asm_secondary_load
asm_diskgroups
asm_power_limit
_asm_log_scale_rebalance
_asm_sync_rebalance
_asm_ausize
_asm_blksize
_asm_acd_chunks
_asm_partner_target_disk_part
_asm_partner_target_fg_rel
_asm_automatic_rezone
_asm_rebalance_plan_size
_asm_rebalance_space_errors
_asm_libraries
_asm_maxio
_asm_allow_only_raw_disks
_asm_fob_tac_frequency
_asm_emulate_nfs_disk
_asmlib_test
_asm_allow_lvm_resilvering
_asm_lsod_bucket_size
_asm_iostat_latch_count
_asm_disable_smr_creation
_asm_wait_time
_asm_skip_resize_check
_asm_skip_rename_check
_asm_direct_con_expire_time
_asm_check_for_misbehaving_cf_clients
_asm_diag_dead_clients
_asm_reserve_slaves
_asm_kill_unresponsive_clients
_asm_disable_async_msgs
_asm_stripewidth
_asm_stripesize
_asm_random_zone
_asm_serialize_volume_rebalance
_asm_force_quiesce
_asm_dba_threshold
_asm_dba_batch
_asm_usd_batch
_asm_fail_random_rx
_asm_max_redo_buffer_size
_asm_max_cod_strides
_asm_kfioevent
_asm_evenread
_asm_evenread_alpha
_asm_evenread_alpha2
_asm_evenread_faststart
_asm_dbmsdg_nohdrchk
_asm_root_directory
_asm_hbeatiowait
_asm_hbeatwaitquantum
_asm_repairquantum
_asm_emulmax
_asm_emultimeout
_asm_kfdpevent
_asm_storagemaysplit
_asm_avoid_pst_scans
_asm_compatibility
_asm_admin_with_sysdba
_asm_allow_appliance_dropdisk_noforce
_asm_appliance_config_file
_disable_rebalance_space_check
_disable_rebalance_compact

 

 

 

_disable_rebalance_compact : Setting _DISABLE_REBALANCE_COMPACT=TRUE will disable the compacting phase of the disk group rebalance.

 

Since version 11.1, the ASM performs a disk compacting once the rebalance is complete.
This may have a noticeable impact on the first rebalance after the upgrade from 10g.
The idea of the compacting phase it to move the data as close the outer tracks of the disks
(the lower numbered offsets) as possible. The first time the rebalance runs in 11g, it could
take a while if the disk group configuration changed – for example after an ALTER
DISKGROUP … ADD DISK. Subsequent manual rebalance without a configuration change
should not take as much time.
A disk group where the compacting phase of the rebalance has done a lot of work will tend to
have better performance than the pre-compact disk group. The data should be clustered near
the higher performing tracks of the disk, and the seek times should be shorter.
Relevant initialization parameter: _DISABLE_REBALANCE_COMPACT.
Relevant disk group attribute: _REBALANCE_COMPACT.
The holemarks of the compacting phase:

  • Rebalance is taking ‘too long’
  • Updates to gv$asm_operation have stopped
  • In the ARB0 trace file we see many lines like this: ARB0 relocating file +<diskgroup>.nnn.mmm (1 entries)
  • Stack (systemstate, processstate or pstack) shows kfdCompact() function.

 

_asm_avoid_pst_scans:

If set, limit the number of full scans (of all disks) we do when reading the
PST in kfdp_readMeta(). This is also required to activate split PST checks
(which rely on the lock value block being available)

 

 

_asm_evenread – enable/disable even read.
0 = Defer to the disk group attribute (to be implemented)
1 = ENABLE (always on)
2 = DISABLE (always off)
18 = Enabled iff offline disks are found
_asm_evenread_tracing – tracing; 0 is off, 1 is 1 line per IO, 3 is verbose
_asm_evenread_alpha -alpha value, x2^14 (16 is a good value)
_asm_evenread_alpha2 – secondary alpha value, x2^14
_asm_evenread_faststart – number of IOs after offline/online to use alpha2 (default 0)

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