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# Configuration Parameters


Before starting to use IoTDB, you need to config the configuration files first. For your convenience, we have already set the default config in the files.

In total, we provide users three kinds of configurations module: 

* environment configuration file (`iotdb-env.bat`, `iotdb-env.sh`). The default configuration file for the environment configuration item. Users can configure the relevant system configuration items of JAVA-JVM in the file.
* system configuration file (`iotdb-engine.properties`). 
	* `iotdb-engine.properties`: The default configuration file for the IoTDB engine layer configuration item. Users can configure the IoTDB engine related parameters in the file, such as JDBC service listening port (`rpc_port`), unsequence data storage directory (`unsequence_data_dir`), etc. What's more, Users can configure the information about the TsFile, such as the data size written to the disk per time(`group_size_in_byte`). 
  
* log configuration file (`logback.xml`)

The configuration files of the three configuration items are located in the IoTDB installation directory: `$IOTDB_HOME/conf` folder.

## Hot Modification Configuration

For the convenience of users, IoTDB server provides users with hot modification function, that is, modifying some configuration parameters in `iotdb engine. Properties` during the system operation and applying them to the system immediately. 
In the parameters described below, these parameters whose way of `Effective` is `trigger` support hot modification.

Trigger way: The client sends the command `load configuration` to the IoTDB server. See Chapter 4 for the usage of the client.

## IoTDB Environment Configuration File

The environment configuration file is mainly used to configure the Java environment related parameters when IoTDB Server is running, such as JVM related configuration. This part of the configuration is passed to the JVM when the IoTDB Server starts. Users can view the contents of the environment configuration file by viewing the `iotdb-env.sh` (or `iotdb-env.bat`) file.

The detail of each variables are as follows:

* MAX\_HEAP\_SIZE

|Name|MAX\_HEAP\_SIZE|
|:---:|:---|
|Description|The maximum heap memory size that IoTDB can use at startup.|
|Type|String|
|Default| On Linux or MacOS, the default is one quarter of the memory. On Windows, the default value for 32-bit systems is 512M, and the default for 64-bit systems is 2G.|
|Effective|After restarting system|

* HEAP\_NEWSIZE

|Name|HEAP\_NEWSIZE|
|:---:|:---|
|Description|The minimum heap memory size that IoTDB can use at startup.|
|Type|String|
|Default| On Linux or MacOS, the default is min{cores * 100M, one quarter of MAX\_HEAP\_SIZE}. On Windows, the default value for 32-bit systems is 512M, and the default for 64-bit systems is 2G.|
|Effective|After restarting system|

* JMX\_LOCAL

|Name|JMX\_LOCAL|
|:---:|:---|
|Description|JMX monitoring mode, configured as yes to allow only local monitoring, no to allow remote monitoring|
|Type|Enum String: "true", "false"|
|Default|true|
|Effective|After restarting system|


* JMX\_PORT

|Name|JMX\_PORT|
|:---:|:---|
|Description|JMX listening port. Please confirm that the port is not a system reserved port and is not occupied|
|Type|Short Int: [0,65535]|
|Default|31999|
|Effective|After restarting system|

* JMX\_IP

|Name|JMX\_IP|
|:---:|:---|
|Description|JMX listening address. Only take effect if JMX\_LOCAL=false. 0.0.0.0 is never allowed|
|Type|String|
|Default|127.0.0.1|
|Effective|After restarting system|

## JMX Authorization

We **STRONGLY RECOMMENDED** you CHANGE the PASSWORD for the JMX remote connection.

The user and passwords are in ${IOTDB\_CONF}/conf/jmx.password.

The permission definitions are in ${IOTDB\_CONF}/conf/jmx.access.

## IoTDB System Configuration File

### File Layer

* compressor

|Name|compressor|
|:---:|:---|
|Description|Data compression method|
|Type|Enum String : “UNCOMPRESSED”, “SNAPPY”|
|Default| UNCOMPRESSED |
|Effective|Trigger|

* group\_size\_in\_byte

|Name|group\_size\_in\_byte|
|:---:|:---|
|Description|The data size written to the disk per time|
|Type|Int32|
|Default| 134217728 |
|Effective|Trigger|

* page\_size\_in\_byte

|Name| page\_size\_in\_byte |
|:---:|:---|
|Description|The maximum size of a single page written in memory when each column in memory is written (in bytes)|
|Type|Int32|
|Default| 65536 |
|Effective|Trigger|

* max\_number\_of\_points\_in\_page

|Name| max\_number\_of\_points\_in\_page |
|:---:|:---|
|Description|The maximum number of data points (timestamps - valued groups) contained in a page|
|Type|Int32|
|Default| 1048576 |
|Effective|Trigger|

* max\_degree\_of\_index\_node

|Name| max\_degree\_of\_index\_node |
|:---:|:---|
|Description|The maximum degree of the metadata index tree (that is, the max number of each node's children)|
|Type|Int32|
|Default| 256 |
|Effective|Only allowed to be modified in first start up|

* max\_string\_length

|Name| max\_string\_length |
|:---:|:---|
|Description|The maximum length of a single string (number of character)|
|Type|Int32|
|Default| 128 |
|Effective|Trigger|

* time\_encoder

|Name| time\_encoder |
|:---:|:---|
|Description| Encoding type of time column|
|Type|Enum String: “TS_2DIFF”,“PLAIN”,“RLE”|
|Default| TS_2DIFF |
|Effective|Trigger|

* value\_encoder

|Name| value\_encoder |
|:---:|:---|
|Description| Encoding type of value column|
|Type|Enum String: “TS_2DIFF”,“PLAIN”,“RLE”|
|Default| PLAIN |
|Effective|Trigger|

* float_precision

|Name| float_precision |
|:---:|:---|
|Description| The precision of the floating point number.(The number of digits after the decimal point) |
|Type|Int32|
|Default| The default is 2 digits. Note: The 32-bit floating point number has a decimal precision of 7 bits, and the 64-bit floating point number has a decimal precision of 15 bits. If the setting is out of the range, it will have no practical significance. |
|Effective|Trigger|


* bloomFilterErrorRate

|Name| bloomFilterErrorRate |
|:---:|:---|
|Description| The false positive rate of bloom filter in each TsFile. Bloom filter checks whether a given time series is in the tsfile before loading metadata. This can improve the performance of loading metadata and skip the tsfile that doesn't contain specified time series. If you want to learn more about its mechanism, you can refer to: [wiki page of bloom filter](https://en.wikipedia.org/wiki/Bloom_filter).|
|Type|float, (0, 1)|
|Default| 0.05 |
|Effective|After restarting system|


* freq_snr

|Name| freq_snr |
|:---:|:---|
|Description| Signal-noise-ratio (SNR) of lossy FREQ encoding |
|Type|Double|
|Default| 40.0 |
|Effective|Trigger|


* freq_block_size

|Name| freq_block_size |
|:---:|:---|
|Description| Block size of FREQ encoding. In other words, the number of data points in a time-frequency transformation. To speed up the encoding, it is recommended to be the power of 2. |
|Type|Int32|
|Default| 1024 |
|Effective|Trigger|

### Engine Layer

* rpc\_address

|Name| rpc\_address |
|:---:|:---|
|Description| The jdbc service listens on the address.|
|Type|String|
|Default| "0.0.0.0" |
|Effective|After restarting system|

* rpc\_port

|Name| rpc\_port |
|:---:|:---|
|Description| The jdbc service listens on the port. Please confirm that the port is not a system reserved port and is not occupied.|
|Type|Short Int : [0,65535]|
|Default| 6667 |
|Effective|After restarting system|

* rpc\_thrift\_compression\_enable

|Name| rpc\_thrift\_compression\_enable |
|:---:|:---|
|Description| Whether enable thrift's compression (using GZIP).|
|Type|Boolean|
|Default| false |
|Effective|After restarting system|

* rpc\_advanced\_compression\_enable

|Name| rpc\_advanced\_compression\_enable |
|:---:|:---|
|Description| Whether enable thrift's advanced compression.|
|Type|Boolean|
|Default| false |
|Effective|After restarting system|


* time\_zone

|Name| time\_zone |
|:---:|:---|
|Description| The time zone in which the server is located, the default is Beijing time (+8) |
|Type|Time Zone String|
|Default| +08:00 |
|Effective|Trigger|

* base\_dir

|Name| base\_dir |
|:---:|:---|
|Description| The IoTDB system folder. It is recommended to use an absolute path. |
|Type|String|
|Default| data |
|Effective|After restarting system|

* data\_dirs

|Name| data\_dirs |
|:---:|:---|
|Description| The directories of data files. Multiple directories are separated by comma. The starting directory of the relative path is related to the operating system. It is recommended to use an absolute path. If the path does not exist, the system will automatically create it.|
|Type|String[]|
|Default| data/data |
|Effective|Trigger|

* wal\_dir

|Name| wal\_dir |
|:---:|:---|
|Description| Write Ahead Log storage path. It is recommended to use an absolute path. |
|Type|String|
|Default| data/wal |
|Effective|After restarting system|

* enable\_wal

|Name| enable\_wal |
|:---:|:---|
|Description| Whether to enable the pre-write log. The default value is true(enabled), and false means closed. |
|Type|Bool|
|Default| true |
|Effective|Trigger|

* enable\_mem\_control

|Name| enable\_mem\_control |
|:---:|:---|
|Description| enable memory control to avoid OOM|
|Type|Bool|
|Default| true |
|Effective|After restarting system|

* memtable\_size\_threshold

|Name| memtable\_size\_threshold |
|:---:|:---|
|Description| max memtable size|
|Type|Long|
|Default| 1073741824 |
|Effective| when enable\_mem\_control is false & After restarting system |

* enable\_timed\_flush\_seq\_memtable

|Name| enable\_timed\_flush\_seq\_memtable |
|:---:|:---|
|Description| whether to enable timed flush sequence memtable |
|Type|Bool|
|Default| false |
|Effective| Trigger |

* seq\_memtable\_flush\_interval\_in\_ms

|Name| seq\_memtable\_flush\_interval\_in\_ms |
|:---:|:---|
|Description| if a memTable's created time is older than current time minus this, the memtable will be flushed to disk |
|Type|Int32|
|Default| 3600000 |
|Effective| Trigger |

* seq\_memtable\_flush\_check\_interval\_in\_ms

|Name| seq\_memtable\_flush\_check\_interval\_in\_ms |
|:---:|:---|
|Description| the interval to check whether sequence memtables need flushing |
|Type|Int32|
|Default| 600000 |
|Effective| Trigger |

* enable\_timed\_flush\_unseq\_memtable

|Name| enable\_timed\_flush\_unseq\_memtable |
|:---:|:---|
|Description| whether to enable timed flush unsequence memtable |
|Type|Bool|
|Default| false |
|Effective| Trigger |

* unseq\_memtable\_flush\_interval\_in\_ms

|Name| unseq\_memtable\_flush\_interval\_in\_ms |
|:---:|:---|
|Description| if a memTable's created time is older than current time minus this, the memtable will be flushed to disk |
|Type|Int32|
|Default| 3600000 |
|Effective| Trigger |

* unseq\_memtable\_flush\_check\_interval\_in\_ms

|Name| unseq\_memtable\_flush\_check\_interval\_in\_ms |
|:---:|:---|
|Description| the interval to check whether unsequence memtables need flushing |
|Type|Int32|
|Default| 600000 |
|Effective| Trigger |

* avg\_series\_point\_number\_threshold

|Name| avg\_series\_point\_number\_threshold                  |
|:---:|:-------------------------------------------------------|
|Description| max average number of point of each series in memtable |
|Type| Int32                                                  |
|Default| 100000                                                 |
|Effective| After restarting system                                |

* tsfile\_size\_threshold

|Name| tsfile\_size\_threshold |
|:---:|:---|
|Description| max tsfile size|
|Type|Long|
|Default| 536870912 |
|Effective| After restarting system |

* enable\_partition

|Name| enable\_partition |
|:---:|:---|
|Description| Whether enable time partition for data, if disabled, all data belongs to partition 0 (it's not recommend to open this function. If open, please calculate appropriate concurrent_writing_time_partition and wal_buffer_size)|
|Type|Bool|
|Default| false |
|Effective|Only allowed to be modified in first start up|

* partition\_interval

|Name| partition\_interval |
|:---:|:---|
|Description| Time range for dividing storage group, time series data will be divided into groups by this time range |
|Type|Int64|
|Default| 604800 |
|Effective|Only allowed to be modified in first start up|


* concurrent\_writing\_time\_partition

|Name| concurrent\_writing\_time\_partition |
|:---:|:---|
|Description| This config decides how many time partitions in a storage group can be inserted concurrently </br> For example, your partitionInterval is 86400 and you want to insert data in 5 different days, |
|Type|Int32|
|Default| 1 |
|Effective|After restarting system|

* multi\_dir\_strategy

|Name| multi\_dir\_strategy |
|:---:|:---|
|Description| IoTDB's strategy for selecting directories for TsFile in tsfile_dir. You can use a simple class name or a full name of the class. The system provides the following three strategies: <br>1. SequenceStrategy: IoTDB selects the directory from tsfile\_dir in order, traverses all the directories in tsfile\_dir in turn, and keeps counting;<br>2. MaxDiskUsableSpaceFirstStrategy: IoTDB first selects the directory with the largest free disk space in tsfile\_dir;<br>3. MinFolderOccupiedSpaceFirstStrategy: IoTDB prefers the directory with the least space used in tsfile\_dir;<br>4. UserDfineStrategyPackage (user-defined policy)<br>You can complete a user-defined policy in the following ways:<br>1. Inherit the cn.edu.tsinghua.iotdb.conf.directories.strategy.DirectoryStrategy class and implement its own Strategy method;<br>2. Fill in the configuration class with the full class name of the implemented class (package name plus class name, UserDfineStrategyPackage);<br>3. Add the jar file to the project. |
|Type|String|
|Default| MaxDiskUsableSpaceFirstStrategy |
|Effective|Trigger|

* tsfile\_size\_threshold

|Name| tsfile\_size\_threshold |
|:---:|:---|
|Description| When a TsFile size on the disk exceeds this threshold, the TsFile is closed and open a new TsFile to accept data writes. The unit is byte and the default value is 2G.|
|Type| Int64 |
|Default| 536870912 |
|Effective|After restarting system|

* tag\_attribute\_total\_size

|Name| tag\_attribute\_total\_size |
|:---:|:---|
|Description| The maximum persistence size of tags and attributes of each time series.|
|Type| Int32 |
|Default| 700 |
|Effective|Only allowed to be modified in first start up|

* tag\_attribute\_flush\_interval

|Name| tag\_attribute\_flush\_interval                                                                                                                                                                                                                |
|:---:|:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|Description| interval num for tag and attribute records when force flushing to disk. When a certain amount of tag and attribute records is reached, they will be force flushed to disk. It is possible to lose at most tag_attribute_flush_interval records |
|Type| Int32                                                                                                                                                                                                                                          |
|Default| 1000                                                                                                                                                                                                                                           |
|Effective| Only allowed to be modified in first start up                                                                                                                                                                                                  |

* enable\_partial\_insert

|Name| enable\_partial\_insert |
|:---:|:---|
|Description| Whether continue to write other measurements if some measurements are failed in one insertion.|
|Type| Bool |
|Default| true |
|Effective|After restarting system|

* mtree\_snapshot\_interval

|Name| mtree\_snapshot\_interval |
|:---:|:---|
|Description| The least interval line numbers of mlog.txt when creating a checkpoint and saving snapshot of MTree. Unit: line numbers|
|Type| Int32 |
|Default| 100000 |
|Effective|After restarting system|

* mlog\_buffer\_size

|Name| mlog\_buffer\_size |
|:---:|:---|
|Description| size of log buffer in each metadata operation plan(in byte) |
|Type|Int32|
|Default| 1048576 |
|Effective|After restart system|

* sync\_mlog\_period\_in\_ms

|Name| sync\_mlog\_period\_in\_ms |
|:---:|:---|
|Description| The cycle when metadata log is periodically forced to be written to disk(in milliseconds). If force_mlog_period_in_ms = 0 it means force metadata log to be written to disk after each refreshment|
|Type| Int64 |
|Default| 100 |
|Effective|After restart system|

* flush\_wal\_threshold

|Name| flush\_wal\_threshold |
|:---:|:---|
|Description| After the WAL reaches this value, it is flushed to disk, and it is possible to lose at most flush_wal_threshold operations. |
|Type|Int32|
|Default| 10000 |
|Effective|Trigger|

* force\_wal\_period\_in\_ms

|Name| force\_wal\_period\_in\_ms |
|:---:|:---|
|Description| The period during which the log is periodically forced to flush to disk(in milliseconds) |
|Type|Int32|
|Default| 10 |
|Effective|Trigger|

* fetch\_size

|Name| fetch\_size |
|:---:|:---|
|Description| The amount of data read each time in batch (the number of data strips, that is, the number of different timestamps.) |
|Type|Int32|
|Default| 10000 |
|Effective|After restarting system|

* enable\_stat\_monitor

|Name| enable\_stat\_monitor |
|:---:|:---|
|Description| Whether to enable background statistics|
|Type| Boolean |
|Default| false |
|Effective|After restarting system|

* concurrent\_flush\_thread

|Name| concurrent\_flush\_thread |
|:---:|:---|
|Description| The thread number used to perform the operation when IoTDB writes data in memory to disk. If the value is less than or equal to 0, then the number of CPU cores installed on the machine is used. The default is 0.|
|Type| Int32 |
|Default| 0 |
|Effective|After restarting system|

* concurrent\_query\_thread

|Name| concurrent\_query\_thread                                                                                            |
|:---:|:---------------------------------------------------------------------------------------------------------------------|
|Description| The thread number which can concurrently execute query statement. When <= 0, use CPU core number. The default is 16. |
|Type| Int32                                                                                                                |
|Default| 16                                                                                                                   |
|Effective| After restarting system                                                                                              |

* concurrent\_sub\_rawQuery\_thread

|Name| concurrent\_sub\_rawQuery\_thread                                                                                        |
|:---:|:-------------------------------------------------------------------------------------------------------------------------|
|Description| The thread number which can concurrently read data for raw data query. When <= 0, use CPU core number. The default is 8. |
|Type| Int32                                                                                                                    |
|Default| 8                                                                                                                        |
|Effective| After restarting system                                                                                                  |

* tsfile\_storage\_fs

|Name| tsfile\_storage\_fs |
|:---:|:---|
|Description| The storage file system of Tsfile and related data files. Currently LOCAL file system and HDFS are supported.|
|Type| String |
|Default|LOCAL |
|Effective|Only allowed to be modified in first start up|

* core\_site\_path

|Name| core\_site\_path |
|:---:|:---|
|Description| Absolute file path of core-site.xml if Tsfile and related data files are stored in HDFS.|
|Type| String |
|Default|/etc/hadoop/conf/core-site.xml |
|Effective|After restarting system|

* hdfs\_site\_path

|Name| hdfs\_site\_path |
|:---:|:---|
|Description| Absolute file path of hdfs-site.xml if Tsfile and related data files are stored in HDFS.|
|Type| String |
|Default|/etc/hadoop/conf/hdfs-site.xml |
|Effective|After restarting system|

* hdfs\_ip

|Name| hdfs\_ip |
|:---:|:---|
|Description| IP of HDFS if Tsfile and related data files are stored in HDFS. **If there are more than one hdfs\_ip in configuration, Hadoop HA is used.**|
|Type| String |
|Default|localhost |
|Effective|After restarting system|

* hdfs\_port

|Name| hdfs\_port |
|:---:|:---|
|Description| Port of HDFS if Tsfile and related data files are stored in HDFS|
|Type| String |
|Default|9000 |
|Effective|After restarting system|

* dfs\_nameservices

|Name| hdfs\_nameservices |
|:---:|:---|
|Description| Nameservices of HDFS HA if using Hadoop HA|
|Type| String |
|Default|hdfsnamespace |
|Effective|After restarting system|

* dfs\_ha\_namenodes

|Name| hdfs\_ha\_namenodes |
|:---:|:---|
|Description| Namenodes under DFS nameservices of HDFS HA if using Hadoop HA|
|Type| String |
|Default|nn1,nn2 |
|Effective|After restarting system|

* dfs\_ha\_automatic\_failover\_enabled

|Name| dfs\_ha\_automatic\_failover\_enabled |
|:---:|:---|
|Description| Whether using automatic failover if using Hadoop HA|
|Type| Boolean |
|Default|true |
|Effective|After restarting system|

* dfs\_client\_failover\_proxy\_provider

|Name| dfs\_client\_failover\_proxy\_provider |
|:---:|:---|
|Description| Proxy provider if using Hadoop HA and enabling automatic failover|
|Type| String |
|Default|org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider |
|Effective|After restarting system|


* hdfs\_use\_kerberos

|Name| hdfs\_use\_kerberos |
|:---:|:---|
|Description| Whether use kerberos to authenticate hdfs|
|Type| String |
|Default|false |
|Effective|After restarting system|

* kerberos\_keytab\_file_path

|Name| kerberos\_keytab\_file_path |
|:---:|:---|
|Description| Full path of kerberos keytab file|
|Type| String |
|Default|/path |
|Effective|After restarting system|

* kerberos\_principal

|Name| kerberos\_principal |
|:---:|:---|
|Description| Kerberos pricipal|
|Type| String |
|Default|your principal |
|Effective|After restarting system|


* authorizer\_provider\_class

|Name| authorizer\_provider\_class |
|:---:|:---|
|Description| the class name of the authorization service|
|Type| String |
|Default|org.apache.iotdb.db.auth.authorizer.LocalFileAuthorizer |
|Effective|After restarting system|
|Other available values| org.apache.iotdb.db.auth.authorizer.OpenIdAuthorizer |

* openID\_url

|Name| openID\_url |
|:---:|:---|
|Description| the openID server if OpenIdAuthorizer is enabled|
|Type| String (a http url) |
|Default|no |
|Effective|After restarting system|

* thrift\_max\_frame\_size

|Name| thrift\_max\_frame\_size |
|:---:|:---|
|Description| the max bytes in a RPC request/response|
|Type| long |
|Default| 536870912 (should >= 512 * 1024 * 1024) |
|Effective|After restarting system|

### InfluxDB-Protocol Adaptor

* enable_influxdb_rpc_service

|    Name     | enable_influxdb_rpc_service            |
| :---------: | :------------------------------------- |
| Description | Whether to enable InfluxDB RPC service |
|    Type     | Boolean                                |
|   Default   | true                                   |
|  Effective  | After restarting system                |

* influxdb_rpc_port

|    Name     | influxdb_rpc_port                     |
| :---------: | :------------------------------------ |
| Description | The port used by InfluxDB RPC service |
|    Type     | INT32                                 |
|   Default   | 8086                                  |
|  Effective  | After restarting system               |

###  Query

* default\_fill\_interval

|    Name     | default\_fill\_interval                         |
| :---------: | :---------------------------------------------- |
| Description | Default interval of `group by fill` query in ms |
|    Type     | Int32                                           |
|   Default   | -1                                              |
|  Effective  | After restarting system                         |

* group_by_fill_cache_size_in_mb

|    Name     | group_by_fill_cache_size_in_mb      |
| :---------: | :---------------------------------- |
| Description | Cache size of `group by fill` query |
|    Type     | Float                               |
|   Default   | 1.0                                 |
|  Effective  | After restarting system             |

### Compaction Config

* enable\_seq\_space\_compaction

|Name| enable\_seq\_space\_compaction |
|:---:|:---|
|Description| enable the compaction between sequence files |
|Type| Boolean |
|Default| true |
|Effective|After restart system|

* enable\_unseq\_space\_compaction

|Name| enable\_unseq\_space\_compaction |
|:---:|:---|
|Description| enable the compaction between unsequence files |
|Type| Boolean |
|Default| false |
|Effective|After restart system|

* enable\_cross\_space\_compaction

|Name| enable\_cross\_space\_compaction |
|:---:|:---|
|Description| enable the compaction between sequence files and unsequence files |
|Type| Boolean |
|Default| true |
|Effective|After restart system|

* cross\_compaction\_strategy

|Name| cross\_compaction\_strategy |
|:---:|:---|
|Description| strategy of cross space compaction |
|Type| String |
|Default| rewrite\_compaction|
|Effective|After restart system|

* inner\_compaction\_strategy

|Name| inner\_compaction\_strategy |
|:---:|:---|
|Description| strategy of inner space compaction |
|Type| String |
|Default| size\_tiered\_compaction |
|Effective|After restart system|

* compaction\_priority

|Name| compaction\_priority |
|:---:|:---|
|Description| Priority of compaction task. When it is BALANCE, system executes all types of compaction equally; when it is INNER_CROSS, system takes precedence over executing inner space compaction task; when it is CROSS_INNER, system takes precedence over executing cross space compaction task |
|Type| String |
|Default| BALANCE|
|Effective|After restart system|

* target\_compaction\_file\_size

|Name| target\_compaction\_file\_size |
|:---:|:---|
|Description| The target file is in inner space compaction |
|Type| Int64 |
|Default| 1073741824 |
|Effective|After restart system|

* target\_chunk\_size

|Name| target\_chunk\_size |
|:---:|:---|
|Description| The target size of compacted chunk |
|Type| Int64 |
|Default| 1048576 |
|Effective|After restart system|

* target\_chunk\_point\_num

|Name| target\_chunk\_point\_num |
|:---:|:---|
|Description| The target point number of compacted chunk |
|Type| Int32 |
|Default| 100000 |
|Effective|After restart system|

* chunk\_size\_lower\_bound\_in\_compaction

|Name| chunk\_size\_lower\_bound\_in\_compaction |
|:---:|:---|
|Description| A source chunk will be deserialized in compaction when its size is less than this value |
|Type| Int64 |
|Default| 128 |
|Effective|After restart system|

* chunk\_point\_num\_lower\_bound\_in\_compaction

|Name| chunk\_size\_lower\_bound\_in\_compaction |
|:---:|:---|
|Description| A source chunk will be deserialized in compaction when its point num is less than this value |
|Type| Int32 |
|Default| 100 |
|Effective|After restart system|

* max\_inner\_compaction\_candidate\_file\_num

|Name| max\_inner\_compaction\_candidate\_file\_num |
|:---:|:---|
|Description| The max num of files encounter in inner space compaction |
|Type| Int32 |
|Default| 30 |
|Effective|After restart system|

* max\_cross\_compaction\_file\_num

|Name| max\_cross\_compaction\_candidate\_file\_num |
|:---:|:---|
|Description| The max num of files encounter in cross space compaction |
|Type| Int32 |
|Default| 1000 |
|Effective|After restart system|

* cross\_compaction\_file\_selection\_time\_budget

|Name| cross\_compaction\_file\_selection\_time\_budget |
|:---:|:---|
|Description| Time budget for cross space compaction file selection |
|Type| Int32 |
|Default| 30000 |
|Effective|After restart system|

* cross\_compaction\_memory\_budget

|Name| cross\_compaction\_memory\_budget |
|:---:|:---|
|Description| Memory budget for a cross space compaction |
|Type| Int32 |
|Default| 2147483648 |
|Effective|After restart system|

* concurrent\_compaction\_thread

|Name| concurrent\_compaction\_thread |
|:---:|:---|
|Description| thread num to execute compaction |
|Type| Int32 |
|Default| 10 |
|Effective|After restart system|

* compaction\_schedule\_interval\_in\_ms

|Name| compaction\_schedule\_interval\_in\_ms |
|:---:|:---|
|Description| interval of scheduling compaction |
|Type| Int64 |
|Default| 60000 |
|Effective|After restart system|

* compaction\_submission\_interval\_in\_ms

|Name| compaction\_submission\_interval\_in\_ms |
|:---:|:---|
|Description| interval of submitting compaction task |
|Type| Int64 |
|Default| 60000 |
|Effective|After restart system|

* compaction\_write\_throughput\_mb\_per\_sec

|Name| compaction\_write\_throughput\_mb\_per\_sec |
|:---:|:---|
|Description| The write rate of all compaction tasks in MB/s |
|Type| Int32 |
|Default| 16 |
|Effective|After restart system|

### Insertion

- insert_multi_tablet_enable_multithreading_column_threshold

|    Name     | insert_multi_tablet_enable_multithreading_column_threshold   |
| :---------: | :----------------------------------------------------------- |
| Description | When the insert plan column count reaches the specified threshold, multi-threading is enabled. |
|    Type     | Int32                                                        |
|   Default   | 10                                                           |
|  Effective  | After restarting system                                      |

### Automatic Schema Creation and Type Inference

* enable\_auto\_create\_schema

|Name| enable\_auto\_create\_schema |
|:---:|:---|
|Description| whether auto create the time series when a non-existed time series data comes|
|Type| true or false |
|Default|true |
|Effective|After restarting system|

* default\_storage\_group\_level

|Name| default\_storage\_group\_level |
|:---:|:---|
|Description| Storage group level when creating schema automatically is enabled. For example, if we receives a data point from root.sg0.d1.s2, we will set root.sg0 as the storage group if storage group level is 1. (root is level 0)|
|Type| integer |
|Default|1 |
|Effective|After restarting system|

* boolean\_string\_infer\_type

|Name| boolean\_string\_infer\_type |
|:---:|:---|
|Description| To which type the values "true" and "false" should be reslved|
|Type| BOOLEAN or TEXT |
|Default|BOOLEAN |
|Effective|After restarting system|

* integer\_string\_infer\_type

|Name| integer\_string\_infer\_type |
|:---:|:---|
|Description| To which type an integer string like "67" in a query should be resolved|
|Type| INT32, INT64, DOUBLE, FLOAT or TEXT |
|Default|DOUBLE |
|Effective|After restarting system|

* nan\_string\_infer\_type

|Name| nan\_string\_infer\_type |
|:---:|:---|
|Description| To which type the value NaN in a query should be resolved|
|Type| DOUBLE, FLOAT or TEXT |
|Default|FLOAT |
|Effective|After restarting system|

* floating\_string\_infer\_type

|Name| floating\_string\_infer\_type |
|:---:|:---|
|Description| To which type a floating number string like "6.7" in a query should be resolved|
|Type| DOUBLE, FLOAT or TEXT |
|Default|FLOAT |
|Effective|After restarting system|

* enable\_partition

|Name| enable\_partition |
|:---:|:---|
|Description| whether enable data partition. If disabled, all data belongs to partition 0|
|Type| BOOLEAN |
|Default|false |
|Effective|Only allowed to be modified in first start up|

* partition\_interval

|Name| partition\_interval |
|:---:|:---|
|Description| time range for partitioning data inside each storage group, the unit is second|
|Type| LONG |
|Default| 604800 |
|Effective|Only allowed to be modified in first start up|

* data\_region\_num

|    Name     | data\_region\_num                                                                                                                                                                                                                                                  |
|:-----------:|:-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | number of data regions per user-defined storage group, a data region is the unit of parallelism in memory as all ingestions in one data region are serialized, recommended value is [data region number] = [CPU core number] / [user-defined storage group number] |
|    Type     | LONG                                                                                                                                                                                                                                                               |
|   Default   | 1                                                                                                                                                                                                                                                                  |
|  Effective  | Only allowed to be modified in first start up                                                                                                                                                                                                                      |

<!--
* enable\_id\_table

|Name| enable\_id\_table |
|:---:|:---|
|Description| whether to use id table. ATTENTION: id table is not compatible with alias |
|Type| bool |
|Default| false |
|Effective|After restarting system|

* device\_id\_transformation\_method

|Name| device\_id\_transformation\_method |
|:---:|:---|
|Description| the method to transform device path to device id, can be 'Plain' or 'SHA256' |
|Type| string |
|Default| Plain |
|Effective|Only allowed to be modified in first start up|

* enable\_id\_table\_log\_file

|Name| enable\_id\_table\_log\_file |
|:---:|:---|
|Description| whether create mapping file of id table. This file can map device id in tsfile to device path |
|Type| bool |
|Default| false |
|Effective|After restarting system|

-->

### UDF

* udf\_initial\_byte\_array\_length\_for\_memory\_control

|    Name     | udf\_initial\_byte\_array\_length\_for\_memory\_control      |
| :---------: | :----------------------------------------------------------- |
| Description | Used to estimate the memory usage of text fields in a UDF query. It is recommended to set this value to be slightly larger than the average length of all texts. |
|    Type     | Int32                                                        |
|   Default   | 48                                                           |
|  Effective  | After restarting system                                      |

* udf\_memory\_budget\_in\_mb

|    Name     | udf\_memory\_budget\_in\_mb                                  |
| :---------: | :----------------------------------------------------------- |
| Description | How much memory may be used in ONE UDF query (in MB). The upper limit is 20% of allocated memory for read. |
|    Type     | Float                                                        |
|   Default   | 30.0                                                         |
|  Effective  | After restarting system                                      |

* udf\_reader\_transformer\_collector\_memory\_proportion

|    Name     | udf\_reader\_transformer\_collector\_memory\_proportion      |
| :---------: | :----------------------------------------------------------- |
| Description | UDF memory allocation ratio for reader, transformer and collector. The parameter form is a : b : c, where a, b, and c are integers. |
|    Type     | String                                                       |
|   Default   | 1:1:1                                                        |
|  Effective  | After restarting system                                      |

* udf\_root\_dir

|    Name     | udf\_root\_dir            |
| :---------: | :------------------------ |
| Description | Root directory of UDF     |
|    Type     | String                    |
|   Default   | ext/udf(Windows:ext\\udf) |
|  Effective  | After restarting system   |

### SELECT-INTO

* select_into_insert_tablet_plan_row_limit

|    Name     | select_into_insert_tablet_plan_row_limit                     |
| :---------: | :----------------------------------------------------------- |
| Description | The maximum number of rows that can be processed in insert-tablet-plan when executing select-into statements. When <= 0, use 10000. |
|    Type     | Int32                                                        |
|   Default   | 10000                                                        |
|  Effective  | Trigger                                                      |

### Trigger

- concurrent_window_evaluation_thread

|    Name     | concurrent_window_evaluation_thread                          |
| :---------: | :----------------------------------------------------------- |
| Description | How many threads can be used for evaluating sliding windows. When <= 0, use CPU core number. |
|    Type     | Int32                                                        |
|   Default   | The number of CPU cores                                      |
|  Effective  | After restarting system                                      |

- max_pending_window_evaluation_tasks

|    Name     | max_pending_window_evaluation_tasks                          |
| :---------: | :----------------------------------------------------------- |
| Description | Maximum number of window evaluation tasks that can be pending for execution. When <= 0, the value is 64 by default. |
|    Type     | Int32                                                        |
|   Default   | 64                                                           |
|  Effective  | After restarting system                                      |

### Continuous Query

- continuous_query_execution_thread

|    Name     | continuous_query_execution_thread                            |
| :---------: | :----------------------------------------------------------- |
| Description | How many threads will be set up to perform continuous queries |
|    Type     | Int32                                                        |
|   Default   | max(1, the / 2)                                              |
|  Effective  | After restarting system                                      |

- max_pending_continuous_query_tasks

|    Name     | max_pending_continuous_query_tasks                           |
| :---------: | :----------------------------------------------------------- |
| Description | Maximum number of continuous query tasks that can be pending for execution |
|    Type     | Int32                                                        |
|   Default   | 64                                                           |
|  Effective  | After restarting system                                      |

- continuous_query_min_every_interval

|    Name     | continuous_query_min_every_interval                 |
| :---------: | :-------------------------------------------------- |
| Description | Minimum every interval to perform continuous query. |
|    Type     | duration                                            |
|   Default   | 1s                                                  |
|  Effective  | After restarting system                             |

## Enable GC log

GC log is off by default.
For performance tuning, you may want to collect the GC info. 

To enable GC log, just add a parameter "printgc" when you start the server.

```bash
nohup sbin/start-server.sh printgc >/dev/null 2>&1 &
```
Or
```bash
sbin\start-server.bat printgc
```

GC log is stored at `IOTDB_HOME/logs/gc.log`.
There will be at most 10 gc.log.* files and each one can reach to 10MB.