# Configuring replication filters with MySQL
You can use replication filters to specify which databases and tables are replicated with a read replica. Replication filters can include databases and tables in replication or exclude them from replication.
The following are some use cases for replication filters:
+ To reduce the size of a read replica. With replication filtering, you can exclude the databases and tables that aren't needed on the read replica.
+ To exclude databases and tables from read replicas for security reasons.
+ To replicate different databases and tables for specific use cases at different read replicas. For example, you might use specific read replicas for analytics or sharding.
+ For a DB instance that has read replicas in different AWS Regions, to replicate different databases or tables in different AWS Regions.
**Note**
You can also use replication filters to specify which databases and tables are replicated with a primary MySQL DB instance that is configured as a replica in an inbound replication topology. For more information about this configuration, see [Configuring binary log file position replication with an external source instance](MySQL.Procedural.Importing.External.Repl.md).
**Topics**
+ [Setting replication filtering parameters for RDS for MySQL](#USER_MySQL.Replication.ReadReplicas.ReplicationFilters.Configuring)
+ [Replication filtering limitations for RDS for MySQL](#USER_MySQL.Replication.ReadReplicas.ReplicationFilters.Limitations)
+ [Replication filtering examples for RDS for MySQL](#USER_MySQL.Replication.ReadReplicas.ReplicationFilters.Examples)
+ [Viewing the replication filters for a read replica](#USER_MySQL.Replication.ReadReplicas.ReplicationFilters.Viewing)
## Setting replication filtering parameters for RDS for MySQL
To configure replication filters, set the following replication filtering parameters on the read replica:
+ `replicate-do-db` – Replicate changes to the specified databases. When you set this parameter for a read replica, only the databases specified in the parameter are replicated.
+ `replicate-ignore-db` – Don't replicate changes to the specified databases. When the `replicate-do-db` parameter is set for a read replica, this parameter isn't evaluated.
+ `replicate-do-table` – Replicate changes to the specified tables. When you set this parameter for a read replica, only the tables specified in the parameter are replicated. Also, when the `replicate-do-db` or `replicate-ignore-db` parameter is set, make sure to include the database that includes the specified tables in replication with the read replica.
+ `replicate-ignore-table` – Don't replicate changes to the specified tables. When the `replicate-do-table` parameter is set for a read replica, this parameter isn't evaluated.
+ `replicate-wild-do-table` – Replicate tables based on the specified database and table name patterns. The `%` and `_` wildcard characters are supported. When the `replicate-do-db` or `replicate-ignore-db` parameter is set, make sure to include the database that includes the specified tables in replication with the read replica.
+ `replicate-wild-ignore-table` – Don't replicate tables based on the specified database and table name patterns. The `%` and `_` wildcard characters are supported. When the `replicate-do-table` or `replicate-wild-do-table` parameter is set for a read replica, this parameter isn't evaluated.
The parameters are evaluated in the order that they are listed. For more information about how these parameters work, see the MySQL documentation:
+ For general information, see [ Replica Server Options and Variables](https://dev.mysql.com/doc/refman/8.0/en/replication-options-replica.html).
+ For information about how database replication filtering parameters are evaluated, see [ Evaluation of Database-Level Replication and Binary Logging Options](https://dev.mysql.com/doc/refman/8.0/en/replication-rules-db-options.html).
+ For information about how table replication filtering parameters are evaluated, see [ Evaluation of Table-Level Replication Options](https://dev.mysql.com/doc/refman/8.0/en/replication-rules-table-options.html).
By default, each of these parameters has an empty value. On each read replica, you can use these parameters to set, change, and delete replication filters. When you set one of these parameters, separate each filter from others with a comma.
You can use the `%` and `_` wildcard characters in the `replicate-wild-do-table` and `replicate-wild-ignore-table` parameters. The `%` wildcard matches any number of characters, and the `_` wildcard matches only one character.
The binary logging format of the source DB instance is important for replication because it determines the record of data changes. The setting of the `binlog_format` parameter determines whether the replication is row-based or statement-based. For more information, see [Configuring RDS for MySQL binary logging for Single-AZ databases](USER_LogAccess.MySQL.BinaryFormat.md).
**Note**
All data definition language (DDL) statements are replicated as statements, regardless of the `binlog_format` setting on the source DB instance.
## Replication filtering limitations for RDS for MySQL
The following limitations apply to replication filtering for RDS for MySQL:
+ Each replication filtering parameter has a 2,000-character limit.
+ Commas aren't supported in replication filters for parameter values. In a list of parameters, commas can only be used as value separators. For example, `ParameterValue='`a,b`'` isn’t supported, but `ParameterValue='a,b'` is.
+ The MySQL `--binlog-do-db` and `--binlog-ignore-db` options for binary log filtering aren't supported.
+ Replication filtering doesn't support XA transactions.
For more information, see [ Restrictions on XA Transactions](https://dev.mysql.com/doc/refman/8.0/en/xa-restrictions.html) in the MySQL documentation.
## Replication filtering examples for RDS for MySQL
To configure replication filtering for a read replica, modify the replication filtering parameters in the parameter group associated with the read replica.
**Note**
You can't modify a default parameter group. If the read replica is using a default parameter group, create a new parameter group and associate it with the read replica. For more information on DB parameter groups, see [Parameter groups for Amazon RDS](USER_WorkingWithParamGroups.md).
You can set parameters in a parameter group using the AWS Management Console, AWS CLI, or RDS API. For information about setting parameters, see [Modifying parameters in a DB parameter group in Amazon RDS](USER_WorkingWithParamGroups.Modifying.md). When you set parameters in a parameter group, all of the DB instances associated with the parameter group use the parameter settings. If you set the replication filtering parameters in a parameter group, make sure that the parameter group is associated only with read replicas. Leave the replication filtering parameters empty for source DB instances.
The following examples set the parameters using the AWS CLI. These examples set `ApplyMethod` to `immediate` so that the parameter changes occur immediately after the CLI command completes. If you want a pending change to be applied after the read replica is rebooted, set `ApplyMethod` to `pending-reboot`.
The following examples set replication filters:
+ [Including databases in replication](#rep-filter-in-dbs-mysql)
+ [Including tables in replication](#rep-filter-in-tables-mysql)
+ [Including tables in replication with wildcard characters](#rep-filter-in-tables-wildcards-mysql)
+ [Excluding databases from replication](#rep-filter-ex-dbs-mysql)
+ [Excluding tables from replication](#rep-filter-ex-tables-mysql)
+ [Excluding tables from replication using wildcard characters](#rep-filter-ex-tables-wildcards-mysql)
**Example Including databases in replication**
The following example includes the `mydb1` and `mydb2` databases in replication.
For Linux, macOS, or Unix:
```
aws rds modify-db-parameter-group \
--db-parameter-group-name myparametergroup \
--parameters "ParameterName=replicate-do-db,ParameterValue='mydb1,mydb2',ApplyMethod=immediate"
```
For Windows:
```
aws rds modify-db-parameter-group ^
--db-parameter-group-name myparametergroup ^
--parameters "ParameterName=replicate-do-db,ParameterValue='mydb1,mydb2',ApplyMethod=immediate"
```
**Example Including tables in replication**
The following example includes the `table1` and `table2` tables in database `mydb1` in replication.
For Linux, macOS, or Unix:
```
aws rds modify-db-parameter-group \
--db-parameter-group-name myparametergroup \
--parameters "ParameterName=replicate-do-table,ParameterValue='mydb1.table1,mydb1.table2',ApplyMethod=immediate"
```
For Windows:
```
aws rds modify-db-parameter-group ^
--db-parameter-group-name myparametergroup ^
--parameters "ParameterName=replicate-do-table,ParameterValue='mydb1.table1,mydb1.table2',ApplyMethod=immediate"
```
**Example Including tables in replication using wildcard characters**
The following example includes tables with names that begin with `order` and `return` in database `mydb` in replication.
For Linux, macOS, or Unix:
```
aws rds modify-db-parameter-group \
--db-parameter-group-name myparametergroup \
--parameters "ParameterName=replicate-wild-do-table,ParameterValue='mydb.order%,mydb.return%',ApplyMethod=immediate"
```
For Windows:
```
aws rds modify-db-parameter-group ^
--db-parameter-group-name myparametergroup ^
--parameters "ParameterName=replicate-wild-do-table,ParameterValue='mydb.order%,mydb.return%',ApplyMethod=immediate"
```
**Example Excluding databases from replication**
The following example excludes the `mydb5` and `mydb6` databases from replication.
For Linux, macOS, or Unix:
```
aws rds modify-db-parameter-group \
--db-parameter-group-name myparametergroup \
--parameters "ParameterName=replicate-ignore-db,ParameterValue='mydb5,mydb6',ApplyMethod=immediate"
```
For Windows:
```
aws rds modify-db-parameter-group ^
--db-parameter-group-name myparametergroup ^
--parameters "ParameterName=replicate-ignore-db,ParameterValue='mydb5,mydb6',ApplyMethod=immediate"
```
**Example Excluding tables from replication**
The following example excludes tables `table1` in database `mydb5` and `table2` in database `mydb6` from replication.
For Linux, macOS, or Unix:
```
aws rds modify-db-parameter-group \
--db-parameter-group-name myparametergroup \
--parameters "ParameterName=replicate-ignore-table,ParameterValue='mydb5.table1,mydb6.table2',ApplyMethod=immediate"
```
For Windows:
```
aws rds modify-db-parameter-group ^
--db-parameter-group-name myparametergroup ^
--parameters "ParameterName=replicate-ignore-table,ParameterValue='mydb5.table1,mydb6.table2',ApplyMethod=immediate"
```
**Example Excluding tables from replication using wildcard characters**
The following example excludes tables with names that begin with `order` and `return` in database `mydb7` from replication.
For Linux, macOS, or Unix:
```
aws rds modify-db-parameter-group \
--db-parameter-group-name myparametergroup \
--parameters "ParameterName=replicate-wild-ignore-table,ParameterValue='mydb7.order%,mydb7.return%',ApplyMethod=immediate"
```
For Windows:
```
aws rds modify-db-parameter-group ^
--db-parameter-group-name myparametergroup ^
--parameters "ParameterName=replicate-wild-ignore-table,ParameterValue='mydb7.order%,mydb7.return%',ApplyMethod=immediate"
```
## Viewing the replication filters for a read replica
You can view the replication filters for a read replica in the following ways:
+ Check the settings of the replication filtering parameters in the parameter group associated with the read replica.
For instructions, see [Viewing parameter values for a DB parameter group in Amazon RDS](USER_WorkingWithParamGroups.Viewing.md).
+ In a MySQL client, connect to the read replica and run the `SHOW REPLICA STATUS` statement.
In the output, the following fields show the replication filters for the read replica:
+ `Replicate_Do_DB`
+ `Replicate_Ignore_DB`
+ `Replicate_Do_Table`
+ `Replicate_Ignore_Table`
+ `Replicate_Wild_Do_Table`
+ `Replicate_Wild_Ignore_Table`
For more information about these fields, see [Checking Replication Status](https://dev.mysql.com/doc/refman/8.0/en/replication-administration-status.html) in the MySQL documentation.