---
title: "CLOB Configuration for DataSync Agent"
canonical: "https://docs.perspectium.com/space/helium/2114549/CLOB%20Configuration%20for%20DataSync%20Agent"
format: markdown
---
By default, the DataSync Agent's maximum column size is   251   characters for character string type columns such as  NVARCHAR .  When the Agent sees a ServiceNow column defined with more than 251 characters, it will create the column as a  CLOB  type in the database the Agent is connected to.  Columns are created with this length and type to ensure all content is preserved from ServiceNow.   Since ServiceNow uses their own translations to map column types they define for “fields” to the column types of the backend database that powers their platform, these fields don’t always have the exact same length as what’s shown in the ServiceNow UI.  When a field is created with  less than 251  characters in ServiceNow, that field is considered a single line string which maps to an  NVARCHAR  type with the same number of characters in the ServiceNow platform's backend database (generally MySQL).  If it’s more than 251 characters, that field would be mapped and created as a  CLOB  type in their backend database.  As a result, when you define a field in ServiceNow with a type of “String” and a length of 400 and  because this is mapped to a  CLOB  type in the backend database, you can actually enter a value greater than 400 characters in the field and it will save properly in ServiceNow both in the UI and in background scripts.  When the data is sent out from ServiceNow using the Perspectium DataSync application, this field’s data will appear with more than 400 characters.   If the agent were to create a column in the database with 400 characters, this would result in the data being truncated and loss of content. To prevent this, the Agent creates the field with a larger length and uses a  CLOB  type that has no length restrictions. The Agent does provide a way to customize this value to a different one than the default value of 251.  To do this, add the following directive to the   agent.xml   file saved in your Agent's installation directory: Directive Value <database_column_max_size> A number to be the maximum before converting to a CLOB. This value cannot be greater than the database maximum size for a character string column (see below).   NOTE :  Each Agent-supported database has a maximum value that a text column can be created as.  Any column size greater than the value specified below will be created as a CLOB type. Database Maximum Column Size Oracle 2000 SQL Server (MSSQL) 4000 MySQL* 4000 SAP Hana 5000 Amazon Redshift 65535 Amazon Aurora 65535 IBM DB2 32672 HP Vertica 65000 PostGreSQL 10485760 Snowflake 4000 Sybase 32767   NOTE :  MySQL  also has  table row size  limits that should be considered before setting this value too high as you may get " Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to TEXT or BLOBs" exceptions if you create too many columns as character string types and not  CLOB  types. The following is an example of the  agent.xml : <?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
<config>
  <agent>
     <max_reads_per_connect>4000</max_reads_per_connect>
     <polling_interval>5</polling_interval>
     <skip_message_set_processing/>
     <share/>
     <subscribe>
        <task instances="1">
           <task_name>test_subscribe</task_name>
           <message_connection password="encrypted:vlOtU71yu8N/EFIJH85SSBtaIt7qEEfvqiqft9VZyYE=" queue="psp.out.replicator.testqueue" user="admin" use_basic_consume="false">https://testperspectium.net</message_connection>
           <instance_connection password="encrypted:vlOtU71yu8N/EFIJH85SSPN9aF0P5/YViVwPEVFcGW4=" user="test.user">https://myinstance.service-now.com</instance_connection>
           <handler>com.perspectium.replicator.sql.SQLSubscriber</handler>
           <decryption_key>This is my decryption key for testing</decryption_key>
           <database_type>mysql</database_type>
           <database_server>localhost</database_server>
           <database_port>3306</database_port>
           <database_user>testuser</database_user>
           <database_password>testpassword</database_password>
           <database_parms>characterEncoding=UTF-8 & useSSL=false</database_parms>
           <database>psp_repl</database>
           <database_column_max_size>4000</database_column_max_size>
        </task>
     </subscribe>
  </agent>
</config> For more information, see  DataSync Agent Configuration   or contact   Perspectium Support . Can't find what you're looking for?     See  the FAQ  or browse the  Perspectium Community Forum .