ISSUE with ColdFusion TRANSACTION and Data Concurrency - coldfusion

Question

I am creating and assigning a value in a variable at the top of the function. But somehow the value gets replaced with other user's table record. This happened when two users doing transaction at same time with different records. Also it is happening only once in a while.
I have mentioned the issue in comments in below code.
<cffunction name="functionname" output="true">
<cfargument name="formData">
<cftransaction action="begin">
<cftry>
<cfquery name="getDoc_no" datasource="#variables.dsn#">
SELECT CONCAT(TO_CHAR(SYSDATE,'YYYY'),WORK_REQ_SEQ.NEXTVAL) as NEXT_NO FROM DUAL
</cfquery>
<cfset doc_no_seq=getDoc_no.NEXT_NO> <!---creating variable doc_no_seq --->
<cfquery name="getWo_no" datasource="#variables.dsn#">
SELECT WORK_ORDER_SEQ.nextval as NEXT_NO FROM DUAL
</cfquery>
<cfset Trns_seq=getWo_no.NEXT_NO> <!--- creating variable Trns_seq --->
<cfquery name="insert1" datasource="#variables.dsn#">
INSERT into WORK_ORDER
(
DOC_NO,
TRANS_ID
)
Values
(
<cfqueryparam value="#doc_no_seq#" cfsqltype="cf_sql_integer">, <!--- Inserted CORRECT doc_no_seq value --->
<cfqueryparam value="#Trns_seq#" cfsqltype="cf_sql_integer"> <!--- Inserted CORRECT Trns_seq value --->
)
</cfquery>
<cfif isdefined("IdnoRes") and IdnoRes gt 0>
<cfloop from="1" to="#IdnoRes#" index="q">
<cfif trim(Evaluate("rsc_grp_id_#q#")) is not "" and trim(Evaluate("qty_#q#")) is not "">
<cfquery name="insert2" datasource="#variables.dsn#">
INSERT into REQ_RESOURCE_DTLS
(
DOC_NO ,
TRANS_ID
)
Values
(
<cfqueryparam value="#doc_no_seq#" cfsqltype="cf_sql_integer">, <!--- Inserted WRONG doc_no_seq value --->
<cfqueryparam value="#Trns_seq#" cfsqltype="cf_sql_integer"> <!--- Inserted WRONG Trns_seq value --->
)
</cfquery>
</cfif>
</cfloop>
</cfif>
<cfif isdefined("Idnojob") and Idnojob gt 0>
<cfloop from="1" to="#Idnojob#" index="q">
<cfif trim(Evaluate("frm_des_#q#")) is not "" and trim(Evaluate("to_des_#q#")) is not "">
<cfquery name="insert3" datasource="#variables.dsn#">
INSERT into JOB_SEQ_DTLS
(
DOC_NO ,
TRANS_ID
)
Values
(
<cfqueryparam value="#doc_no_seq#" cfsqltype="cf_sql_integer">, <!--- Inserted WRONG doc_no_seq value --->
<cfqueryparam value="#Trns_seq#" cfsqltype="cf_sql_integer"> <!--- Inserted WRONG Trns_seq value --->
)
</cfquery>
</cfif>
</cfloop>
</cfif>
<cftransaction action="commit" />
<cfcatch type="any">
<cftransaction action="rollback" />
</cfcatch>
</cftry>
</cftransaction>
<cfreturn 1>