grails 2.3.7 data binding how assign database in multiple database

Question

I am using grails 2.3.7 multiple database i am configured.in save databinding working fine.but update has occur issue table not found error

Domain class : PurchaseItem.groovy

class PurchaseItem {

    String item

   static mapping = { 
        datasource 'ALL'

    }
}

PurchaseRequest.groovy

class PurchaseRequest {

    String prCode

    static hasMany = [purchaseItems:PurchaseItem]

        static mapping = { 
        datasource 'ALL'

    }
}

controller : PurchaseRequestController.groovy

import static org.springframework.http.HttpStatus.*
import grails.transaction.Transactional

@Transactional(readOnly = true)
class PurchaseRequestController {


    @Transactional
    def save(PurchaseRequest purchaseRequestInstance) {

        purchaseRequestInstance.demodatabase.save flush:true

        render "success"

  }

    @Transactional
    def update() {

        def purchaseRequestInstance = PurchaseRequest.demodatabase.get(params.id)

        purchaseRequestInstance.properties = params       

        purchaseRequestInstance.demodatabase.save failOnError:true
        render "Success"
    }
}

Error:

Field error in object 'testmuliple.PurchaseRequest' on field 'purchaseItems': rejected value [1]; codes [testmuliple.PurchaseRequest.purchaseItems.typeMismatch.error,testmuliple.PurchaseRequest.purchaseItems.typeMismatch,purchaseRequest.purchaseItems.typeMismatch.error,purchaseRequest.purchaseItems.typeMismatch,typeMismatch.testmuliple.PurchaseRequest.purchaseItems,typeMismatch.purchaseItems,typeMismatch.java.util.Set,typeMismatch]; arguments [purchaseItems]; default message [Illegal attempt to update element in [purchaseItems] Set with id [1]. No such record was found.]