今天执行一条expdp语句时，报错如下：
ORA-31626: job does not exist
ORA-31633: unable to create master table "NEW.GWJOB"
ORA-06512: at "SYS.DBMS_SYS_ERROR", line 95
ORA-06512: at "SYS.KUPV$FT", line 1020
ORA-00955: name is already used by an existing object
因为我上次执行这个expdp命令的时候，在命令执行完之前手动kill了这个命令，导致Oracle没有自动清除表gwjob。
如果正常执行，oracle会自动清除这个表。
这个表记录了执行这个命令的详细信息，表结构如下：
Name Null? Type
----------------------------------------- -------- ----------------------------
PROCESS_ORDER NUMBER
DUPLICATE NUMBER
DUMP_FILEID NUMBER
DUMP_POSITION NUMBER
DUMP_LENGTH NUMBER
DUMP_ORIG_LENGTH NUMBER
DUMP_ALLOCATION NUMBER
COMPLETED_ROWS NUMBER
ERROR_COUNT NUMBER
ELAPSED_TIME NUMBER
OBJECT_TYPE_PATH VARCHAR2(200)
OBJECT_PATH_SEQNO NUMBER
OBJECT_TYPE VARCHAR2(30)
IN_PROGRESS CHAR(1)
OBJECT_NAME VARCHAR2(500)
OBJECT_LONG_NAME VARCHAR2(4000)
OBJECT_SCHEMA VARCHAR2(30)
ORIGINAL_OBJECT_SCHEMA VARCHAR2(30)
ORIGINAL_OBJECT_NAME VARCHAR2(4000)
PARTITION_NAME VARCHAR2(30)
SUBPARTITION_NAME VARCHAR2(30)
DATAOBJ_NUM NUMBER
FLAGS NUMBER
PROPERTY NUMBER
TRIGFLAG NUMBER
CREATION_LEVEL NUMBER
COMPLETION_TIME DATE
OBJECT_TABLESPACE VARCHAR2(30)
SIZE_ESTIMATE NUMBER
OBJECT_ROW NUMBER
PROCESSING_STATE CHAR(1)
PROCESSING_STATUS CHAR(1)
BASE_PROCESS_ORDER NUMBER
BASE_OBJECT_TYPE VARCHAR2(30)
BASE_OBJECT_NAME VARCHAR2(30)
BASE_OBJECT_SCHEMA VARCHAR2(30)
ANCESTOR_PROCESS_ORDER NUMBER
DOMAIN_PROCESS_ORDER NUMBER
PARALLELIZATION NUMBER
UNLOAD_METHOD NUMBER
LOAD_METHOD NUMBER
GRANULES NUMBER
SCN NUMBER
GRANTOR VARCHAR2(30)
XML_CLOB CLOB
PARENT_PROCESS_ORDER NUMBER
NAME VARCHAR2(30)
VALUE_T VARCHAR2(4000)
VALUE_N NUMBER
IS_DEFAULT NUMBER
FILE_TYPE NUMBER
USER_DIRECTORY VARCHAR2(4000)
USER_FILE_NAME VARCHAR2(4000)
FILE_NAME VARCHAR2(4000)
EXTEND_SIZE NUMBER
FILE_MAX_SIZE NUMBER
PROCESS_NAME VARCHAR2(30)
LAST_UPDATE DATE
WORK_ITEM VARCHAR2(30)
OBJECT_NUMBER NUMBER
COMPLETED_BYTES NUMBER
TOTAL_BYTES NUMBER
METADATA_IO NUMBER
DATA_IO NUMBER
CUMULATIVE_TIME NUMBER
PACKET_NUMBER NUMBER
INSTANCE_ID NUMBER
OLD_VALUE VARCHAR2(4000)
SEED NUMBER
LAST_FILE NUMBER
USER_NAME VARCHAR2(30)
OPERATION VARCHAR2(30)
JOB_MODE VARCHAR2(30)
QUEUE_TABNUM NUMBER
CONTROL_QUEUE VARCHAR2(30)
STATUS_QUEUE VARCHAR2(30)
REMOTE_LINK VARCHAR2(4000)
VERSION NUMBER
JOB_VERSION VARCHAR2(30)
DB_VERSION VARCHAR2(30)
TIMEZONE VARCHAR2(64)
STATE VARCHAR2(30)
PHASE NUMBER
GUID RAW(16)
START_TIME DATE
BLOCK_SIZE NUMBER
METADATA_BUFFER_SIZE NUMBER
DATA_BUFFER_SIZE NUMBER
DEGREE NUMBER
PLATFORM VARCHAR2(101)
ABORT_STEP NUMBER
INSTANCE VARCHAR2(60)
CLUSTER_OK NUMBER
SERVICE_NAME VARCHAR2(100)
OBJECT_INT_OID VARCHAR2(32)
当然，解决这个错误就很简单了，直接删除这个表就可以了。
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