I/O parameters|V3.2.4|OceanBase Database| docs|Distributed Database

I/O parameters

Last Updated：2023-10-24 09:23:03 Updated

Parameter	Description	Suggested value/range
syslog_io_bandwidth_limit	The maximum process log printing bandwidth.	Suggested value: 10 MB. The default value is 30 MB.
syslog_level	The system log level.	PERF for performance scenarios.
clog_sync_time_warn_threshold	The threshold of log synchronization time for reporting an alert in the log.	We recommend that you set it to a larger value. However, note that a large value may affect the investigation into slow clog synchronization issues.
trace_log_slow_query_watermark	The threshold of transaction execution time for the generation of slow trans logs.	We recommend that you set this parameter to a large value to avoid the generation of trace logs for slow queries.
max_syslog_file_count	The maximum allowed number of observers.log files. The log files are automatically recycled when the specified number is reached.	We recommend that you adjust the value based on the disk space.
merge_thread_count	The number of scheduling threads for major compactions. Default value: 10.	You may set it to a larger value as needed.
enable_sql_operator_dump	Specifies whether to allow SQL layer operations such as hash join to dump intermediate results. Enabling this feature helps avoid memory overflow errors.	We recommend that you enable it for AP testing.
_temporary_file_io_area_size	The total size of intermediate SQL (such as hash join) results at the storage layer.	We recommend that you set it to a larger value for AP testing.
builtin_db_data_verify_cycle	The macroblock inspection cycle. Inspection is disabled if the value is set to 0.	We recommend that you set this parameter to 0 for performance scenarios.
data_copy_concurrency	The maximum number of concurrent data migration and replication tasks.	We recommend that you increase the value for backup and recovery or migration and replication tasks.
server_data_copy_in_concurrency	The number of threads for inbound replica migration.	We recommend that you increase the value for backup and recovery or migration and replication tasks.
server_data_copy_out_concurrency	The number of threads for outbound replica migration.	We recommend that you increase the value for backup and recovery or migration and replication tasks.
disk_io_thread_count	The number of disk I/O threads. The value must be an even number.	You may adjust the value based on the I/O load.
enable_async_syslog	Specifies whether to enable asynchronous logs.	We recommend that you set the value to True for performance scenarios.
enable_clog_persistence_compress	Whether to enable clog storage compression for higher disk flushing efficiency. This parameter reduces the I/O resource consumed for disk flushing of clogs. However, it increases the compression overhead before disk flushing.	We recommend that you enable this feature for systems with limited Clog disk space. In performance scenarios, we recommend that you do not enable the feature.
fuse_row_cache_priority	The priority of the fuse row cache in the KV cache. OceanBase Database features a multi-level storage architecture. For a query of a row with multiple columns in the MemStore, mini SSTable, minor SSTable, and SSTable, OceanBase Database needs to fuse these columns. In this case, the fuse row cache is used to cache the row, so that OceanBase Database no longer needs to fuse the row for subsequent queries. The cache has some effect on performance.	We recommend that you set it to a value greater than 1 to avoid premature replacement of this cache.
merge_stat_sampling_ratio	The statistics sampling rate in a major compaction. Statistics collection is disabled when it is set to 0.	In performance scenarios, you can be set to 0 or 1 to reduce sampling during major compactions.
micro_block_merge_verify_level	The macroblock verification level. The value 0 indicates no verification.	In performance scenarios, you can set it to 0. However, we do not recommend that you change the default value in a production system.
sys_bkgd_io_high_percentage	The allowed maximum percentage of system background I/Os.	To ensure that background tasks, such as minor compactions and major compactions, are properly performed, the background I/O must have a write bandwidth of at least 128 MB.
sys_bkgd_io_low_percentage	The allowed minimum percentage of system background I/Os.	To ensure that background tasks, such as minor compactions and major compactions, are properly performed, the background I/O must have a write bandwidth of at least 128 MB.