# Reserved Engine Variables The following engine variables are currently reserved for internal use only: | Variable Name | Note | | -------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `activity_tracking_id` | | | `aggregator_id` | | | `allow_point_in_time_attach` | | | `allow_unsafe_bottomless_commands` | | | `allow_unsupported_filesystem` | | | `alter_signal_timeout` | | | `analyze_batch_size` | | | `as_aggregator` | | | `as_leaf` | | | `attach_force_skip_execution_errors` | | | `attach_rebalance_delay_seconds` | | | `auditlogsdir` | | | `auto_attach` | | | `auto_increment_increment` | | | `auto_increment_offset` | | | `auto_replicate` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `back_log` | | | `background_statistics_collection_interval` | | | `background_statistics_collection_threshold` | | | `backup_signal_timeout` | | | `binary_serialization` | | | `bind_address` | | | `blob_cache_sync_interval` | | | `bottomless_cloud_debug_tracing` | | | `bottomless_incremental_autostats_collection_threshold` | | | `bottomless_storage_location` | | | `buffered_rows` | | | `change_count_write_interval` | | | `character_set_client` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `character_set_connection` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `character_set_database` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `character_set_filesystem` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `character_set_results` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `character_set_system` | The character set used to store identifiers. The value is read-only and always has the value`utf8`. | | `clamp_histogram_date_estimates` | | | `clear_orphan_databases_on_attach` | | | `cloud_permissions` | | | `columnar_segment_rows` | Deprecated alias to`columnstore_segment_rows`. | | `columnstore_disk_insert_threshold` | | | `columnstore_json_trace_schema` | | | `columnstore_row_value_table_lock_threshold` | | | `columnstore_sample_per_partition_limit` | | | `columnstore_small_blob_combination_threshold` | | | `command_loop` | | | `compile_metadata_parallel` | | | `convert_nonunique_hash_to_skiplist` | | | `date_format` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `datetime_format` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `datetime_precision_mode` | | | `deadlock_avoidance_strategy` | | | `debug` | | | `debug_mode` | | | `default_autostats_columnstore_cardinality_mode` | | | `default_autostats_columnstore_sampling` | | | `default_autostats_histogram_mode` | | | `default_autostats_rowstore_cardinality_mode` | | | `default_columnstore_table_lock_threshold` | | | `default_max_histogram_buckets` | | | `default_spill_dependent_outputters` | | | `default_week_format` | | | `defaults_file` | | | `disable_cluster_variables` | | | `disable_general_logging` | | | `disable_histogram_estimation` | | | `disable_sampling_estimation` | | | `disable_sampling_estimation_with_histograms` | | | `disable_subquery_merge_with_straight_joins` | | | `disable_update_delete_distributed_transactions` | | | `display_full_estimation_stats` | | | `distributed_connect_timeout` | | | `distributed_heartbeat_timeout` | | | `distributed_optimizer_estimated_restricted_search_cost_bound` | | | `distributed_optimizer_max_join_size` | | | `distributed_optimizer_min_join_size_run_initial_heuristics` | | | `distributed_optimizer_nodes` | | | `distributed_optimizer_old_selectivity_table_threshold` | | | `distributed_optimizer_run_legacy_heuristic` | | | `distributed_optimizer_selectivity_fallback_threshold` | | | `distributed_optimizer_unrestricted_search_threshold` | | | `distributed_optimizer_verbose` | | | `div_precision_increment` | | | `dont_convert_error_rolled_back_xact` | | | `durability` | | | `enable_auto_profile` | | | `enable_background_flusher` | By setting the value of this variable to \`0\`, the background flusher will not be able to flush to disk which will result in memory pressure.Refer to[Configuring the Columnstore to Work Effectively](https://docs.singlestore.com/db/v9.1/create-a-database/configuring-the-columnstore-to-work-effectively.md)for more information. | | `enable_background_merger` | | | `enable_background_statistics_collection` | | | `enable_binary_protocol` | | | `enable_blob_cache_sync_thread` | | | `enable_bottomless` | | | `enable_broadcast_left_join` | | | `enable_distributed_tracing` | | | `enable_histogram_to_unwrap_literals` | | | `enable_ir_cache` | | | `enable_local_shuffle_group_by` | | | `enable_multipartition_queries` | | | `enable_resource_pool_security` | | | `enable_sites` | | | `enable_skiplist_sampling_for_selectivity` | | | `enable_sort_on_load` | | | `end_tags_on_all_databases` | | | `error_count` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `estimate_zero_rows_when_sampling_data_is_missing` | | | `exclude_scalar_subselects_from_filters` | | | `experimental_csi_join_threshold` | | | `experimental_disable_multipartition_parallel_read` | | | `expire_root_password` | | | `explain_joinplan_costs` | | | `exporter_password` | | | exporter\_path | This variable is deprecated and non-operational. | | `exporter_ssl_key_passphrase` | | | `external_auth_tracing_time_limit` | | | `external_functions_whitelist` | | | `external_user` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `failover_initial_grace_interval_seconds` | | | `failover_maximum_grace_interval_seconds` | | | `force_bloom_filters` | | | `force_bushy_joins` | | | `force_heuristic_rewrites` | | | `force_table_pushdown` | | | `foreign_key_checks` | | | `forward_aggregator_plan_hash` | | | `general_log_file` | | | `geo_query_info` | | | `group_concat_max_len` | | | `hash_groupby_segment_distinct_values_threshold` | | | `have_openssl` | | | `have_query_cache` | | | `have_ssl` | | | `heartbeat_max_connection_saturation_timeout_ms` | | | `heartbeat_minimum_query_per_sec` | | | `heartbeat_period_ms` | | | `heartbeat_ping_failure_timeout_s` | | | `heartbeats_failed_before_node_failure` | | | `heartbeats_failed_before_reconnect` | | | `http_api_close_connection_on_user_drop` | | | `idle_thread_lifetime_seconds` | | | `ignore_builtin_innodb` | | | `ignore_insert_into_computed_column` | | | `init_connect` | | | `init_memsql_db_only` | | | `inlist_precision_limit` | | | `innodb_buffer_pool_size` | | | `innodb_lock_wait_timeout` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `innodb_strict_mode` | | | `insecure_accept_any_password_for_all_users` | | | `interactive_timeout` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `internal_allow_leaf_alters` | | | `internal_allow_systable_queries` | | | `internal_autostats_refresh_enabled` | | | `internal_cluster_replication_provision_timeout_retries` | | | `internal_columnstore_idle_flush_wait_seconds` | | | `internal_columnstore_ingest_aggressive_throttle_ms` | | | `internal_columnstore_max_uncompressed_rowindex_blob_size` | | | `internal_columnstore_validate_blob_after_write` | | | `internal_columnstore_validate_blob_before_read` | | | `internal_columnstore_window_minimum_blob_size` | | | `internal_drop_all_from_plancache_legacy_behavior` | | | `internal_dump_bitcode_file` | | | `internal_dump_clean_bitcode_file` | | | `internal_dump_raw_bitcode_file` | | | `internal_enable_parallel_query_throttling` | | | `internal_extra_sync_replication_logging` | | | `internal_info_schema_show_hidden_tables` | | | `internal_keepalive_count` | | | `internal_keepalive_timeout` | | | `internal_llvm_compile_externally` | | | `internal_llvm_detect_cpu_features` | | | `internal_master_flush` | | | `internal_max_cte_depth` | | | `internal_minimum_local_size_for_llvm_lifetimes` | | | `internal_send_prehandshake_packet` | | | `internal_session_tracelogs_limit` | | | `internal_set_keepalive_on_connections` | | | `internal_set_user_timeout_on_connections` | | | `internal_slave_flush` | | | `internal_specialize_common_opcodes` | | | `internal_trace_compile_args` | | | `interp_first_auto_gen_helper` | | | `interpreter_mode_sampling_threshold` | | | `join_buffer_size` | | | `json_agg_max_len` | | | `lc_messages` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `lc_time_names` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `leaf_pushdown_default` | | | `leaf_pushdown_enable_rowcount` | | | `license` | | | `license_visibility` | | | `llvm_diagnostic_info` | | | `local_file_system_access_restricted` | | | `local_infile` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `lock_logging_min_latency` | | | `lock_upgrade` | | | `locked_in_memory` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `log_error` | | | `log_error_verbosity` | | | `log_output` | | | `log_queries_not_using_indexes` | | | `log_warnings` | | | `lower_case_table_names` | | | `materialize_ctes` | | | `max_broadcast_tree_rowcount` | | | `max_complex_type_elim_rowcount` | | | `max_connect_errors` | | | `max_error_count` | | | `max_heap_table_size` | | | `max_join_size` | | | `max_length_for_sort_data` | | | `max_recursive_cte_iterations` | | | `max_seeks_for_key` | | | `max_sort_length` | | | `max_subselect_aggregator_rowcount` | | | `max_user_connections` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `max_xact_cache_size_aggs` | | | `max_xact_cache_size_leaves` | | | `mbcc_phase_times` | | | `memsql_custom_build` | | | `memsql_license` | | | `minimum_core_count` | | | `minimum_memory_mb` | | | `ml_model` | | | `multi_range_count` | | | `multistatement_transactions` | This variable is deprecated and its value is ignored started in version 8.5. | | `net_retry_count` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `num_workers_background_tasks_pool` | | | `old` | | | `old_local_join_optimizer` | | | `old_passwords` | | | `openssl_version` | | | `optimize_constants` | | | `optimize_expressions_larger_than` | | | `optimize_huge_expressions` | | | `optimize_mpl_before_printing` | | | `optimize_scopes` | | | `optimize_stmt_threshold` | | | `optimizer_beam_width` | | | `optimizer_cross_join_cost` | | | `optimizer_disable_operator_tree_nullability_check` | | | `optimizer_disable_right_join` | | | `optimizer_disable_semi_join_reduction` | | | `optimizer_disable_subselect_to_join` | | | `optimizer_empty_tables_limit` | | | `optimizer_enable_json_text_matching` | | | `optimizer_gb_placement_table_limit` | | | `optimizer_hash_join_cost` | | | `optimizer_latest` | | | `optimizer_merge_join_cost` | | | `optimizer_nested_join_cost` | | | `optimizer_num_partitions` | | | `optimizer_prune_level` | | | `optimizer_search_depth` | | | `optimizer_switch` | | | `optimizer_warnings` | | | `password_expiration_seconds` | | | `password_expiration_mode` | | | `password_history_count` | | | `pipelines_extractor_get_offsets_timeout_ms` | | | `pipelines_extractor_idle_timeout_ms` | | | `plancachedir` | | | `port_open_timeout` | | | `pre_handshake_packet_wait_period_ms` | | | `preload_buffer_size` | | | `preserve_original_colstore_json` | | | `profile_for_debug` | | | `proxy_user` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `quadratic_rewrite_size_limit` | | | `query_alloc_block_size` | | | `query_cache_size` | | | `query_cache_type` | | | `query_prealloc_size` | | | `query_rewrite_loop_iterations` | | | `read_buffer_size` | | | `read_only` | | | `recovery_batch_size` | | | `ref_repl_mgmt_threads` | | | `repartition_minimum_buffer_size` | | | `repl_mgmt_threads` | | | `replication_sync` | This variable has been deprecated and is no longer operational inSingleStore. | | `replication_timeout_ms` | | | `report_mpl_optimizations` | | | `reported_hostname` | | | `reshuffle_group_by_base_cost` | | | `rewrite_verbose` | | | `row_lock_conflict_forces_implicit_rollback` | | | `rows_per_period` | | | `sampling_estimates_for_complex_filters` | | | `secure_auth` | | | `secure_mode` | | | `selectivity_estimation_min_sample_size` | | | `session_lock` | | | `set_global_variables_allowed_list` | | | `singlebox_optimizer_cost_based_threshold` | | | `skip_blob_crc_checks` | | | `skip_create_database_resource_check` | | | `skip_host_cache` | | | `skip_networking` | | | `skip_rebalance_blob_cache_warmup` | | | `skip_rebalance_resource_check` | | | `skip_show_database` | | | `slow_launch_time` | | | `sql_auto_is_null` | | | `sql_mode` | | | `sql_notes` | | | `sql_safe_updates` | | | `ssl_key_passphrase` | | | `statistics_warnings` | | | `strict_mode` | | | `strict_passwords` | | | `subquery_merge_with_outer_joins` | | | `sync2_timeout` | | | `sync_binlog` | | | `synchronize_bottomless_timeout_ms` | | | `synchronize_database_timeout` | | | `syslog_level` | | | `syslog_level_CONSENSUS` | | | `syslog_level_CSI` | | | `syslog_level_CS_QE` | | | `syslog_level_LOAD_DATA_INTERNAL_COMPRESSION` | | | `syslog_level_MCTE` | | | `syslog_level_METADATA` | | | `syslog_level_NETWORK` | | | `syslog_level_PARAMETRIZER` | | | `syslog_level_REPL` | | | `syslog_level_SEND_ERROR` | | | `syslog_level_SPARSE_COMPRESSION` | | | `syslog_level_TRANSACTIONS` | | | `syslog_level_WASM` | | | `syslog_location` | | | `syslog_protocol` | | | `target_replica_blob_cache_size_ratio` | | | `time_format` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `tmp_table_size` | | | `tmpdir` | | | `tracelog_level` | When a`tracelog_level_*`variable is set, each component traces to a separate`memsql_$COMPONENT.log`file. Many of these files will be empty and all of them are meant for internal SingleStore use only. | | `tracelog_level_CONSENSUS` | | | `tracelog_level_CSI` | | | `tracelog_level_CS_QE` | | | `tracelog_level_LOAD_DATA_INTERNAL_COMPRESSION` | | | `tracelog_level_MCTE` | | | `tracelog_level_METADATA` | | | `tracelog_level_NETWORK` | | | `tracelog_level_PARAMETRIZER` | | | `tracelog_level_REPL` | | | `tracelog_level_SEND_ERROR` | | | `tracelog_level_SPARSE_COMPRESSION` | | | `tracelog_level_TRANSACTIONS` | | | `tracelog_level_WASM` | | | `tracelogsdir` | | | `track_leaked_memory` | | | `transaction_read_only` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `tx_read_only` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `udf_gc_expiry` | | | `udf_gc_interval` | | | `unique_checks` | | | `upgrade_skip_sync_repl_step` | | | `use_avx2` | | | `use_bind_address_for_outgoing` | | | `use_column_correlation` | | | `use_joincolumnstore` | | | `use_joincolumnstore_bailout` | | | `use_joincolumnstore_hash` | | | `use_joincolumnstore_trace` | | | `use_memfd_create` | | | `use_popcnt_instruction` | | | `use_seekable_json` | | | `v3_license_path` | | | `verify_column_compression` | | | `verify_fields_in_transitivity` | | | `version` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. To check the version ofSingleStoreyou are running, use the`memsql_version`variable instead. | | `version_comment` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `wait_die_retry_until_timeout_on_die` | | | `wait_timeout` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | | `warning_count` | This variable exists for backwards compatibility with MySQL and is non-operational inSingleStore. | *** Modified at: November 24, 2025 Source: [/db/v9.1/reference/configuration-reference/engine-variables/reserved-engine-variables/](https://docs.singlestore.com/db/v9.1/reference/configuration-reference/engine-variables/reserved-engine-variables/) (An index of the documentation is available at /llms.txt)