一、錯誤提示：
> EXP-00008: Oracle error 4031 encountered
> ORA-04031: unable to allocate 4096 bytes of shared memory
("shared pool","BEGIN :EXEC_STR := SYS.DBMS...","PL/SQL MPCODE","BAMIMA: Bam Buffe
二、錯誤原因：
共享內(nèi)存太小，存在一定碎片，沒有有效的利用保留區(qū)，造成無法分配合適的共享區(qū)。
三、解決步驟：
1.查看當前環(huán)境
SQL> show sga
Total System Global Area 566812832 bytes
Fixed Size 73888 bytes
Variable Size 28811264 bytes
Database Buffers 536870912 bytes
Redo Buffers 1056768 bytes
show parameter shared_pool
NAME TYPE VALUE
------------------------------------ ------- -----
shared_pool_reserved_size string 1048576
shared_pool_size string 20971520
SQL> select sum(free_space) from v$shared_pool_reserved;
SUM(FREE_SPACE)
---------------
1048576
我們可以看到?jīng)]有合理利用保留區(qū)
SQL> SELECT SUM(RELOADS)/SUM(PINS) FROM V$LIBRARYCACHE;
SUM(RELOADS)/SUM(PINS)
----------------------
.008098188
不算太嚴重
SQL> SELECT round((B.Value/A.Value)*100,1) hardpaseperc
FROM V$SYSSTAT A,
V$SYSSTAT B
WHERE A.Statistic# = 171
AND B.Statistic# = 172
AND ROWNUM = 1;
hardpaseperc
------------------
26.5
2.查看保留區(qū)使用情況
SQL> SELECT FREE_SPACE,
FREE_COUNT,
REQUEST_FAILURES,
REQUEST_MISSES,
LAST_FAILURE_SIZE
FROM V$SHARED_POOL_RESERVED;
FREE_SPACE FREE_COUNT REQUEST_FAILURES REQUEST_MISSES LAST_FAILURE_SIZE
---------- ---------- ---------------- -------------- -----------------
1048576 1 146 0 4132
最近一次申請共享區(qū)失敗時該對象需要的共享區(qū)大小4132
select name from v$db_object_cache where sharable_mem = 4132;
name
----------------
dbms_lob
-- dbms_lob正是exp時申請保留區(qū)的對象
3.查看導致?lián)Q頁的應(yīng)用
SQL> select * from x$ksmlru where ksmlrsiz>0;
ADDR INDX INST_ID KSMLRCOM KSMLRSIZ KSMLRNUM KSMLRHON KSMLROHV KSMLRSES
50001A88 0 1 BAMIMA: Bam Buffer 4100 64 DBMS_DDL 402745060 730DEB9C
50001ACC 1 1 BAMIMA: Bam Buffer 4108 736 DBMS_SYS_SQL 1909768749 730D0838
50001B10 2 1 BAMIMA: Bam Buffer 4112 1576 STANDARD 2679492315 730D7E20
50001B54 3 1 BAMIMA: Bam Buffer 4124 1536 DBMS_LOB 853346312 730DA83C
50001B98 4 1 BAMIMA: Bam Buffer 4128 3456 DBMS_UTILITY 4041615653 730C5FC8
50001BDC 5 1 BAMIMA: Bam Buffer 4132 3760 begin :1 := dbms_lob.getLeng... 2942875191 730CFFCC
50001C20 6 1 state objects 4184 1088 0 00
50001C64 7 1 library cache 4192 488 EXU8VEW 2469165743 730C1C68
50001CA8 8 1 state objects 4196 16 0 730C0B90
50001CEC 9 1 state objects 4216 3608 0 730D0838
3.分析各共享池的使用情況
SQL> select KSPPINM,KSPPSTVL
from x$ksppi,
x$ksppcv
where x$ksppi.indx = x$ksppcv.indx
and KSPPINM = '_shared_pool_reserved_min_alloc';
KSPPINM KSPPSTVL
------------------------------- --------
_shared_pool_reserved_min_alloc 4400 --(門值)
我們看到INDX=5,DBMS_LOB造成換頁(就是做exp涉及到lob對象處理造成的換頁情況),換出
最近未使用的內(nèi)存,但是換出內(nèi)存并合并碎片后在共享區(qū)仍然沒有合適區(qū)來存放數(shù)據(jù),說明共享
區(qū)小和碎片過多，然后根據(jù)_shared_pool_reserved_min_alloc的門值來申請保留區(qū),而門值為4400,
所以不符合申請保留區(qū)的條件,造成4031錯誤。
我們前面看到保留區(qū)全部為空閑狀態(tài),所以我們可以
減低門值，使更多申請共享內(nèi)存比4400小的的對象能申請到保留區(qū)，而不造成4031錯誤。
4.解決辦法：
1).增大shared_pool （在不DOWN機的情況下不合適）
2).打patch （在不DOWN機的情況下不合適）
3).減小門值 （在不DOWN機的情況下不合適）
因為LAST_FAILURE_SIZE<_shared_pool_reserved_min_alloc所以表明沒有有效的使用保留區(qū)
SQL> alter system set "_shared_pool_reserved_min_alloc" = 4000;
alter system set "_shared_pool_reserved_min_alloc"=4000
*
ERROR at line 1:
ORA-02095: specified initialization parameter cannot be modified
-- 9i的使用方法alter system set "_shared_pool_reserved_min_alloc"=4000 scope=spfile;
4).使用alter system flush shared_pool; (不能根本性的解決問題)
5).使用dbms_shared_pool.keep
5.由于數(shù)據(jù)庫不能DOWN機，所以只能選擇3)和4)
運行dbmspool.sql
SQL> @/home/oracle/PRodUCts/8.1.7/rdbms/admin/dbmspool.sql
找出需要keep到共享內(nèi)存的對象
SQL> select a.OWNER,
a.name,
a.sharable_mem,
a.kept,
a.EXECUTIONS ,
b.address,
b.hash_value
from v$db_object_cache a,
v$sqlarea b
where a.kept = 'NO' and
(( a.EXECUTIONS > 1000
and a.SHARABLE_MEM > 50000)
or a.EXECUTIONS > 10000)
and SUBSTR(b.sql_text,1,50) = SUBSTR(a.name,1,50);
OWNER NAME SHARABLE_MEM KEP EXECUTIONS ADDRESS HASH_VALUE
------- ----------------------—--- ------------ --- ---------- -------- ----------
SELECT COUNT(OBJECT_ID) 98292 NO 103207 74814BF8 1893309624
FROM ALL_OBJECTS
WHERE OBJECT_NAME = :b1
AND OWNER = :b2
STANDARD 286632 NO 13501
DBMS_LOB 98292 NO 103750
DBMS_LOB 47536 NO 2886542
DBMS_LOB 11452 NO 2864757
DBMS_PICKLER 10684 NO 2681194
DBMS_PICKLER 5224 NO 2663860
SQL> execute dbms_shared_pool.keep('STANDARD');
SQL> execute dbms_shared_pool.keep('74814BF8,1893309624','C');
SQL> execute dbms_shared_pool.keep('DBMS_LOB');
SQL> execute dbms_shared_pool.keep('DBMS_PICKLER');
SQL> select OWNER, name, sharable_mem,kept,EXECUTIONS from v$db_object_cache where kept = 'YES' ORDER BY sharable_mem;
SQL> alter system flush shared_pool;
System altered.
SQL> SELECT POOL,BYTES FROM V$SGASTAT WHERE NAME ='free memory';
POOL BYTES
----------- ----------
shared pool 7742756
large pool 614400
java pool 32768
[oracle@ali-solution oracle]$ sh /home/oracle/admin/dbexp.sh
[oracle@ali-solution oracle]$ grep ORA- /tmp/exp.tmp
未發(fā)現(xiàn)錯誤，導出數(shù)據(jù)成功
四、建議：
由于以上解決的方法是在不能DOWN機的情況下，所以沒能動態(tài)修改初始化參數(shù)，
但問題的本質(zhì)是共享區(qū)內(nèi)存過小，需要增加shared pool，使用綁定變量，才能根本
的解決問題，所以需要在適當?shù)臅r候留出DOWN機時間，對內(nèi)存進行合理的配置。
