Column size in database can be altered based on the corresponding Salesforce field size during DBSync Replication. This functionality is applicable for data types text, number or currency.
To enable this feature, please follow the below steps.
Edit system.propertiesunder<<install-folder>>\dbsync-repl\WEB-INF\db\confand include the command alter.schema.size=true
When alter.schema.size=false, this feature will be disabled.