The set value of the Oracle EXPDP parallel parameter does not correspond to the number of generated files ____oracle

The following experiment opens 4 parallel execution EXPDP, but only 2 export files.

Job:sys_export_full_04 Owner:sys
Operation:export
Creator Privs:true
guid:350d6aa85b202fb4e053991b200ae817
Start Time:sunday, June, 2016 11:32:11
Mode:full
Instance:orcl
Max Parallelism:4
EXPORT Job Parameters:
Parameter Name Parameter Value:
Client_command/******** as SYSDBA dumpfile=full_rw%u.dmp DIRECTORY=EXPDP full=yparallel=4Logfile=expdp20160612.log Cluster=no
State:executing
Bytes processed:4,221,861,952
Percent done:15
Current Parallelism:4
Job Error count:0
Dump File:/expdp/full_rw01.dmp
Bytes written:4,221,874,176
Dump File:/expdp/full_rw%u.dmp

Worker 1 Status:
Process name:dw04
State:executing
Object Schema:sysman
Object Name:mgmt_loader_q_n
Object Type:database_export/schema/post_schema/procobj
Completed Objects:6
Total Objects:6
Worker parallelism:1

Worker 2 Status:
Process Name:dw05
State:executing
Object Schema:test
Object NAME:LOG_FM1
Object Type:database_export/schema/table/table_data
Completed Objects:3
Total objects:61,618
Worker parallelism:1

Worker 3 Status:
Process name:dw06
State:executing
Object Schema:test
Object NAME:LOG_FM1
Object Type:database_export/schema/table/table_data
Completed Objects:2
Total objects:61,618
Worker parallelism:1

Worker 4 Status:
Process name:dw07
State:executing
Object Schema:test
Object NAME:LOG_FM1
Object Type:database_export/schema/table/table_data
Completed Objects:2
Total objects:61,618
Worker parallelism:1


export> status
Job:sys_export_full_04
Operation:export
Mode:full
State:executing
Bytes processed:10,538,498,576
Percent done:41
Current Parallelism:4
Job Error count:0
Dump File:/expdp/full_rw01.dmp
Bytes written:10,631,065,600
Dump File:/expdp/full_rw%u.dmp

Worker 1 Status:
Process name:dw04
State:executing
Object Schema:test2
Object NAME:STD_SZ2
Object Type:database_export/schema/table/table_data
Completed objects:4
Total objects:61,618
Worker parallelism:1

Worker 2 Status:
Process Name:dw05
State:executing
Object Schema:test2
Object NAME:STD_HA3
Object Type:database_export/schema/table/table_data
Completed objects:7
Total objects:61,618
Worker parallelism:1

Worker 3 Status:
Process name:dw06
State:executing
Object Schema:test2
Object NAME:HA_JSM3
Object Type:database_export/schema/table/table_data
Completed Objects:6
Total objects:61,618
Worker parallelism:1

Worker 4 Status:
Process name:dw07
State:executing
Object Schema:test2
Object Name:sz_sjs
Object Type:database_export/schema/table/table_data
Completed Objects:6
Total objects:61,618
Worker parallelism:1

[Oracle@lk expdp]$ Du-sh *
8.0K Expdp20160612.log
18G full_rw01.dmp
4.0K full_rw02.dmp
[Oracle@lk expdp]$ tail-f Expdp20160612.log
. . Exported "SYSTEM". " Repcat$_template_refgroups "0 KB 0 rows
. . Exported "SYSTEM". " Repcat$_template_sites "0 KB 0 rows
. . Exported "SYSTEM". " Repcat$_template_targets "0 KB 0 rows
. . Exported "SYSTEM". " Repcat$_user_authorizations "0 KB 0 rows
. . Exported "SYSTEM". " Repcat$_user_parm_values "0 KB 0 rows
. . Exported "SYSTEM". " Sqlplus_product_profile "0 KB 0 rows
Master table "SYS". " Sys_export_full_04 "Successfully loaded/unloaded
******************************************************************************
Dump file set for SYS. Sys_export_full_04 is:
/expdp/full_rw01.dmp
Job "SYS". Sys_export_full_04 "successfully completed at Sun June 12:02:26 2016 elapsed 0 00:30:15

[Oracle@lk expdp]$ Du-sh *
5.9M Expdp20160612.log
21G Full_rw01.dmp
4.0K full_rw02.dmp
[Oracle@lk expdp]$