同事导出数据，结果遇到如下报错：

expdp user1/XXXXXXXX directory=szdata1 dumpfile=szhzinfo_20180319.dmp logfile=szhzinfo_20180319.log exclude=STATISTICS,INDEX tables=TKINFO QUERY=\"WHERE  voteproccesstime between 20180304000000 and 20180304235959 \"

Processing object type DATABASE_EXPORT/SCHEMA/POST_SCHEMA/PROCACT_SCHEMA

ORA-31693: Table data object "USER1"."TKINFO" failed to load/unload and is being skipped due to error:

ORA-29913: error in executing ODCIEXTTABLEPOPULATE callout

ORA-01555: snapshot too old: rollback segment number with name "" too small

ORA-22924: snapshot too old

遇到ORA-01555报错最直接的反应就是undo表空间大小是否足够，undo_retention参数是否设置太小

经过验证，均不是以上问题造成的.

由于该表格有BLOB类型的列，经过搜索MOS怀疑是BLOB有损坏

IF: ORA-1555 Error During Export on LOB Data (文档 ID 1950937.1)

LOBs and ORA-01555 troubleshooting (文档 ID 846079.1)

开始排查是否有LOB字段的行存在损坏：

1.创建表存放lob损坏行的rowid

SQL> create table corrupted_lob_data (corrupt_rowid rowid, err_num number);

SQL> DESC LOBDATA

Name Null? Type

---------- --------- ------------

ID NOT NULL NUMBER

DOCUMENT BLOB

2.执行如下plsql块，找出存在损坏lob的行

declare

error_1578 exception;

error_1555 exception;

error_22922 exception;

pragma exception_init(error_1578,-1578);

pragma exception_init(error_1555,-1555);

pragma exception_init(error_22922,-22922);

n number;

begin

for cursor_lob in (select rowid r, &&lob_column from &table_owner..&table_with_lob) loop

begin

n := dbms_lob.instr (cursor_lob.&&lob_column, hextoraw ('889911')) ;

exception

when error_1578 then

insert into corrupted_lob_data values (cursor_lob.r, 1578);

commit;

when error_1555 then

insert into corrupted_lob_data values (cursor_lob.r, 1555);

commit;

when error_22922 then

insert into corrupted_lob_data values (cursor_lob.r, 22922);

commit;

end;

end loop;

end;

/

Enter value for lob_column: BYTE_IMAGE

Enter value for table_owner: USER1

Enter value for table_with_lob: TKINFO

old 10: for cursor_lob in (select rowid r, &&lob_column from &table_owner..&table_with_lob) loop

new 10: for cursor_lob in (select rowid r, BYTE_IMAGE from USER1.TKINFO) loop

old 12: num := dbms_lob.instr (cursor_lob.&&lob_column, hextoraw ('889911')) ;

new 12: num := dbms_lob.instr (cursor_lob.BYTE_IMAGE, hextoraw ('889911')) ;

3.查询结果发现rowid为AAAhS4AAUAAE3IRAAC的行 blob列有损坏

SQL> select * from corrupt_lobs;

CORRUPT_ROWID ERR_NUM

------------------ ----------

AAAhS4AAUAAE3IRAAC 1555

修改导出语句，跳过blob损坏的行，重新导出，成功导出

expdp user1/XXXXXXXX directory=szdata1 dumpfile=szhzinfo_20180319.dmp logfile=szhzinfo_20180319.log exclude=STATISTICS,INDEX tables=TKINFO QUERY=\"WHERE rowid NOT IN \(\'AAAhS4AAUAAE3IRAAC\'\) and voteproccesstime between 20180304000000 and 20180304235959 \"