kingbase 关闭 ora_input_emptystr_isnull ora4031 实例关闭

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epeppanda 2024-04-26 18:21:10

话题讨论：
1.ORA-4031是Oracle中最令人厌恶的报错，它的出现有哪几种原因？

2.一旦出现4031错误。也就是说共享池内存不足的情况下，我们该怎样释放内存呢？你有木有遇到过对应的情形呢？请回顾下当时是怎样解决的？

3.有一句俗语叫丢车保帅。运行计划是SQL核心关键所在。是否意味着在释放内存时，不应该覆盖运行计划这部分？当运行计划部分占用内存比較多时，怎样优化呢？

4.消耗共享池内存的主要有两种对象，一种是SQL，而是存储过程、函数、包等这类可运行对象。当遇到4031错误时，您认为须要优先释放哪种对象

问题分析:

1、ORA-4031错误的原因，通常是大量的hard parse导致了shared pool中的free list中产生大量的内存小碎片，当一个须要非常大内存来进行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中的全部内存清空。

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：

假设在结果中发现一系列只字面值不同的SQL，则能够改动cursor_sharing參数：

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;

假设结果大于0，则能够调大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')将使用内存非常大的对象keep在内存中：

先要运行：@?/rdbms/admin/dbmspool.sql

SQL> @?/rdbms/admin/dbmspool.sql

Package created.

Grant succeeded.

View created.

Package body created.

再查出须要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）添加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同意的最大值，改动必须重新启动；

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.

Column	Datatype	Description
SHARED_POOL_SIZE_FOR_ESTIMATE	NUMBER	Shared pool size for the estimate (in megabytes)
SHARED_POOL_SIZE_FACTOR	NUMBER	Size factor with respect to the current shared pool size
ESTD_LC_SIZE	NUMBER	Estimated memory in use by the library cache (in megabytes)
ESTD_LC_MEMORY_OBJECTS	NUMBER	Estimated number of library cache memory objects in the shared pool of the specified size
ESTD_LC_TIME_SAVED	NUMBER	Estimated elapsed parse time saved (in seconds), owing to library cache memory objects being found in a shared pool of the specified size. This is the time that would have been spent in reloading the required objects in the shared pool had they been aged out due to insufficient amount of available free memory.
ESTD_LC_TIME_SAVED_FACTOR	NUMBER	Estimated parse time saved factor with respect to the current shared pool size
ESTD_LC_LOAD_TIME	NUMBER	Estimated elapsed time (in seconds) for parsing in a shared pool of the specified size
ESTD_LC_LOAD_TIME_FACTOR	NUMBER	Estimated load time factor with respect to the current shared pool size
ESTD_LC_MEMORY_OBJECT_HITS	NUMBER	Estimated number of times a library cache memory object was found in a shared pool of the specified size

能够使用以下的SQL语句来预估shared pool的大小：

select 'Shared Pool' component,shared_pool_size_for_estimate estd_sp_size,estd_lc_time_saved_factor parse_time_factor,case when current_parse_time_elapsed_s + adjustment_s<0

then 0 else current_parse_time_elapsed_s + adjustment_s end response_time

from (

select shared_pool_size_for_estimate,shared_pool_size_factor,estd_lc_time_saved_factor,a.estd_lc_time_saved,e.value/100

current_parse_time_elapsed_s,c.estd_lc_time_saved - a.estd_lc_time_saved adjustment_s from v$shared_pool_advice a,

(select * from v$sysstat where name='parse time elapsed') e,

(select estd_lc_time_saved from v$shared_pool_advice where shared_pool_size_factor=1) c

);

COMPONENT ESTD_SP_SIZE PARSE_TIME_FACTOR RESPONSE_TIME

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

Shared Pool 64 .9989 294.37

Shared Pool 72 1 257.37

Shared Pool 80 1.0009 226.37