Oracle datapump expdp/impdp hang

Hang has recently been used to export schema-level data and has to stop the current export job. If you have similar problems, please continue to read it.

1. Problem Description
The database is hang when the entire schema is exported, as shown below:
The symbol ">" is sent once every 300 seconds set by SecureCRT.
Oracle @ Dev-DB-04: ~> Expdp goex_admin/xxx directory = db_dump_dir dumpfile = gobo2.dmp logfile = gobo2.log schemas = goex_admin

Export: Release 10.2.0.4.0-64bit Production on Thursday, 23 May, 2013 9:30:52

Copyright (c) 2003,200 7, Oracle. All rights reserved.

Connected to: Oracle Database 10g Release 10.2.0.4.0-64bit Production
Starting "GOEX_ADMIN". "SYS_EXPORT_SCHEMA_01": goex_admin/******** directory = db_dump_dir dumpfile = gobo2.dmp
Logfile = gobo2.log schemas = goex_admin
>>>>

--> There is no result for querying operations that take a long time. That is to say, datapump does not do anything at all.
Goex_admin @ GOBO2> @ long_ops

No rows selected

--> Query the table of objects generated by a job. The table exists.
Goex_admin @ GOBO2> @ datapump_master_tb

STATUS OBJECT_ID OBJECT_TYPE OWNER_OBJECT
--------------------------------------------------------------------------------------
VALID 315838 TABLE GOEX_ADMIN.SYS_EXPORT_SCHEMA_01

2. Problem Solving
The fixed_date parameter causes the database to be imported and exported by hang [ID 563171.1].
Goex_admin @ GOBO2> show parameter fixed

NAME TYPE VALUE
-----------------------------------------------------------------------------
Fixed_date string 20130506 16:00:00

-- Author: Robinson

Goex_admin @ GOBO2> alter system set fixed_date = none;

System altered.

--> After the fixed_date parameter is removed, the export is normal.
Oracle @ Dev-DB-04: ~> Expdp goex_admin/xxx directory = db_dump_dir dumpfile = gobo2.dmp logfile = gobo2.log schemas = goex_admin

Export: Release 10.2.0.4.0-64bit Production on Thursday, 23 May, 2013 9:30:52

Copyright (c) 2003,200 7, Oracle. All rights reserved.

Connected to: Oracle Database 10g Release 10.2.0.4.0-64bit Production
Starting "GOEX_ADMIN". "SYS_EXPORT_SCHEMA_01": goex_admin/******** directory = db_dump_dir dumpfile = gobo2.dmp
Logfile = gobo2.log schemas = goex_admin
>>>>
Estimate in progress using BLOCKS method...
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
Total estimation using BLOCKS method: 89.31 MB
Processing object type SCHEMA_EXPORT/USER
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
.......................
Processing object type SCHEMA_EXPORT/POST_SCHEMA/PROCACT_SCHEMA
.. Exported "GOEX_ADMIN". "GO_GA_CUST_TBL" 148.4 KB 551 rows
.. Exported "GOEX_ADMIN". "GO_GA_ACC_TBL" 167.9 KB 533 rows

3. FIXED_DATE
FIXED_DATE enables you to set a constant date that SYSDATE will always return instead of the current date.
To undo a fixed date setting, specify FIXED_DATE = NONE. This parameter is useful primarily for testing.
The value can be in the format shown above or in the default Oracle date format, without a time.

The FIXED_DATE parameter can define the current date as a constant and does not change with the system date. It is usually used for testing purposes.
When using datapump for import and export, you should consider setting this parameter to none to avoid the problem of hang import and export.
Versions affected by this parameter: Version 10.1.0.2 to 11.2.0.3