1. ORA-4031错误的原因,一般是大量的hard parse导致了shared pool中的free list中产生大量的内存小碎片,当一个需要很大内存来进行hard parse的sql语句到来时,无法从free list中找到内存,即使进行内存的释放,还是不能找到符合的内存块。从而报ORA-4031错误。
2. ORA-4031错误的解决方法:
1)alter system flush shared_pool;将shared pool中的所有内存清空。该方法治标不治本。
2)共享SQL语句:规范SQL语句的书写;使用绑定变量;找到没有使用绑定变量的SQL:
select sql_fulltext from v$sql where executions=1 order by sql_text;
如果在结果中发现一系列仅仅字面值不同的SQL,则可以修改cursor_sharing参数:
alter system set cursor_sharing = 'force'; 来强制使用绑定变量。
3)使用shared pool中的保留区:
select request_misses from v$shared_pool_reserved;
如果结果大于0,则可以调大shared_pool_reserved的大小;
SQL> show parameter shared_pool
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
shared_pool_reserved_size big integer 4M
shared_pool_size big integer 0
alter system set shared_pool_reserved=xxM scope=both;
4)使用dbms_shared_pool.keep('对象名')将使用内存很大的对象keep在内存中:
先要执行:@?/rdbms/admin/dbmspool.sql
SQL> @?/rdbms/admin/dbmspool.sql
Package created.
Grant succeeded.
View created.
Package body created.
再查出需要keep的对象:
SQL> select owner,name,namespace,type,sharable_mem from v$db_object_cache where sharable_mem>10000
2 and (type='PACKAGE' or type='PACKAGE BODY' or type='FUNCTION' or type='PROCEDURE') and kept='NO';
OWNER NAME NAMESPACE TYPE SHARABLE_MEM
---------- ------------------------- ------------------ --------------- ------------
SYS DBMS_BACKUP_RESTORE TABLE/PROCEDURE PACKAGE 33215
SYSMAN EMD_COLLECTION BODY PACKAGE BODY 33233
SYS DBMS_SHARED_POOL BODY PACKAGE BODY 12644
SYS SYS$RAWTOANY TABLE/PROCEDURE FUNCTION 12640
SYSMAN EMD_MAINTENANCE TABLE/PROCEDURE PACKAGE 29030
SYSMAN EMD_MAINTENANCE BODY PACKAGE BODY 62930
SYSMAN MGMT_JOB_ENGINE BODY PACKAGE BODY 218914
SYSMAN EM_PING BODY PACKAGE BODY 29086
SYS DBMS_BACKUP_RESTORE BODY PACKAGE BODY 95519
SYSMAN EMD_LOADER TABLE/PROCEDURE PACKAGE 12641
SYSMAN EMD_LOADER BODY PACKAGE BODY 71861
SYS PRVT_HDM BODY PACKAGE BODY 43624
SYSMAN MGMT_JOB_ENGINE TABLE/PROCEDURE PACKAGE 24938
SYS STANDARD BODY PACKAGE BODY 24960
SYSMAN EM_SEVERITY_REPOS BODY PACKAGE BODY 33236
SYS PRVT_ADVISOR TABLE/PROCEDURE PACKAGE 12640
SYSMAN MGMT_GLOBAL TABLE/PROCEDURE PACKAGE 29902
SYS DBMS_STANDARD TABLE/PROCEDURE PACKAGE 24929
SYS DBMS_ADVISOR BODY PACKAGE BODY 25000
SYS PRVT_HDM TABLE/PROCEDURE PACKAGE 16732
SYS PRVT_ADVISOR BODY PACKAGE BODY 66780
SYS DBMS_RCVMAN TABLE/PROCEDURE PACKAGE 43295
SYS STANDARD TABLE/PROCEDURE PACKAGE 438648
SYS DBMS_RCVMAN BODY PACKAGE BODY 375759
24 rows selected.
5)增加shared_pool_size的大小:
SQL> select component,current_size from v$sga_dynamic_components;
COMPONENT CURRENT_SIZE
---------------------------------------------------------------- ------------
shared pool 75497472
large pool 4194304
java pool 4194304
streams pool 0
DEFAULT buffer cache 130023424
KEEP buffer cache 0
RECYCLE buffer cache 0
DEFAULT 2K buffer cache 0
DEFAULT 4K buffer cache 0
DEFAULT 8K buffer cache 0
DEFAULT 16K buffer cache 0
DEFAULT 32K buffer cache 0
ASM Buffer Cache 0
13 rows selected.
sga_max_size:SGA允许的最大值,修改必须重启;
sga_target:必须小于sga_max_size, 表示当前SGA的最大值;
alter system set shared_pool_size=xxM scope=both;
3. 使用V$SHARED_POOL_ADVICE来设置shared pool的大小
V$SHARED_POOL_ADVICE displays information about estimated parse time in the shared pool for different pool sizes. The sizes range from 10% of the current shared pool size or the amount of pinned library cache memory (whichever is higher) to 200% of the current shared pool size, in equal intervals. The value of the interval depends on the current size of the shared pool.
可以使用下面的SQL语句来预估shared pool的大小:
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