diff --git a/src/main/java/cokr/xit/adds/biz/nims/service/bean/BizNimsServiceBean.java b/src/main/java/cokr/xit/adds/biz/nims/service/bean/BizNimsServiceBean.java
index de38832..1b5b6e7 100644
--- a/src/main/java/cokr/xit/adds/biz/nims/service/bean/BizNimsServiceBean.java
+++ b/src/main/java/cokr/xit/adds/biz/nims/service/bean/BizNimsServiceBean.java
@@ -5,6 +5,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.CopyOnWriteArrayList;
 
 import javax.validation.Validation;
 import javax.validation.Validator;
@@ -618,6 +619,9 @@ public class BizNimsServiceBean extends AbstractServiceBean implements BizNimsSe
 
 		// 2. 참조사용자보고번호가 있는 경우 처리(rptTyCd : 1 - 취소, 2 - 변경)
 		String errMsg = null;
+		// thread safe 하도록 CopyOnWriteArrayList 사용
+		// List 사용시 java.util.ConcurrentModificationException 발생 - 동시성 문제
+		CopyOnWriteArrayList<NimsApiDto.DsuseRptInfo> concurrentList = new CopyOnWriteArrayList<>(rtnList);
 		for (NimsApiDto.DsuseRptInfo dto : newList) {
 			dto.setRgtr(reqDto.getUserId());
 
@@ -633,16 +637,15 @@ public class BizNimsServiceBean extends AbstractServiceBean implements BizNimsSe
 
 			// FIXME : API 적용 필요
 			// 결과 return 대상 데이타 List에서 조회한 변경 대상이 있는 경우 replace
-			for(NimsApiDto.DsuseRptInfo d : rtnList){
-				if(d.getOrgUsrRptIdNo().equals(dto.getOrgUsrRptIdNo())
-					&& d.getUsrRptIdNo().equals(dto.getRefUsrRptIdNo())){
-					rtnList.remove(d);
-
-					rtnList.add(dto);
-				};
+			for(NimsApiDto.DsuseRptInfo item : concurrentList){
+				if(item.getOrgUsrRptIdNo().equals(dto.getOrgUsrRptIdNo())
+					&& item.getUsrRptIdNo().equals(dto.getRefUsrRptIdNo())){
+					concurrentList.remove(item);
+					concurrentList.add(dto);
+				}
 			}
 		}
-		return rtnList;
+		return new ArrayList<>(concurrentList);
 	}
 
 	private List<NimsApiDto.DsuseRptInfo> findNimsDsuseRptsOfApi(NimsApiRequest.DsuseRptInfoReq reqDto) {
diff --git a/src/main/resources/sql/mapper/biz/nims-mysql-mapper.xml b/src/main/resources/sql/mapper/biz/nims-mysql-mapper.xml
index 35cfed1..0e6cf19 100644
--- a/src/main/resources/sql/mapper/biz/nims-mysql-mapper.xml
+++ b/src/main/resources/sql/mapper/biz/nims-mysql-mapper.xml
@@ -631,7 +631,7 @@
             #{dsuseProcessDe},
             #{orgUsrRptIdNo},
             (SELECT dept_cd FROM tb_user WHERE user_acnt = #{rgtr}),
-            IF(#{rptTyCd} = '1', 'N', 'Y'),
+            'Y',
             DATE_FORMAT(now(), '%Y%m%d%H%i%s'),
             #{rgtr}
         )
@@ -691,7 +691,7 @@
              , mdfcn_dt = DATE_FORMAT(now(), '%Y%m%d%H%i%s')
              , mdfr = #{rgtr}
          WHERE usr_rpt_id_no = #{refUsrRptIdNo}
-           AND use_yn = 'Y'
+           -- AND use_yn = 'Y'
     </update>
 
     <select id="recusiveRefUsrRptIdNo" parameterType="string" resultType="map">