标签归档：In Memory

如何估算表In-Memory需要内存大小

发表于 2014 年 11 月 12 日 由 惜分飞

对于12.1.0.2的In-Memory特性很多朋友都已经知晓,现在可能有这个困惑我一张表启用In-Memory大概需要多少内存呢？该如何估算这个值呢？这里我告诉你通过dbms_compression可以完成你想做的事情
启用In-Memory功能

[oracle@www.xifenfei.com u02]$ sqlplus / as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Thu Aug 7 17:50:47 2014

Copyright (c) 1982, 2014, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL> show parameter inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_max_populate_servers        integer     0
inmemory_query                       string      ENABLE
inmemory_size                        big integer 0
inmemory_trickle_repopulate_servers_ integer     1
optimizer_inmemory_aware             boolean     TRUE

SQL> alter system set inmemory_size=400M;
alter system set inmemory_size=400M
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-02095: specified initialization parameter cannot be modified

SQL>  alter system set inmemory_size=400M scope=spfile;

System altered.

SQL> show pdbs;

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 PDB1                           READ WRITE NO
         4 PDB2                           READ WRITE NO
SQL> alter session set container=pdb1;

Session altered.

SQL> show parameter inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_max_populate_servers        integer     0
inmemory_query                       string      ENABLE
inmemory_size                        big integer 0
inmemory_trickle_repopulate_servers_ integer     1
optimizer_inmemory_aware             boolean     TRUE

SQL> alter system set inmemory_size=200M;
alter system set inmemory_size=200M
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-02095: specified initialization parameter cannot be modified


SQL> alter system set inmemory_size=200M scope=spfile;
alter system set inmemory_size=200M scope=spfile
                                               *
ERROR at line 1:
ORA-02096: specified initialization parameter is not modifiable with this
option


SQL> !oerr ora 2096
02096, 00000, "specified initialization parameter is not modifiable with this option"
// *Cause: Though the initialization parameter is modifiable, it cannot be
//         modified using the specified command.
// *Action: Check the DBA guide for information about under what scope
//          the parameter may be modified



SQL> select 200*1024*1024 from dual;

200*1024*1024
-------------
    209715200

SQL>  alter system set inmemory_size=209715200;
 alter system set inmemory_size=209715200
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-02095: specified initialization parameter cannot be modified


SQL> shutdown immediate;
Pluggable Database closed.
SQL> conn / as sysdba
Connected.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area  838860800 bytes
Fixed Size                  2929936 bytes
Variable Size             360712944 bytes
Database Buffers           50331648 bytes
Redo Buffers                5455872 bytes
In-Memory Area            419430400 bytes
Database mounted.
Database opened.
SQL> show parameter inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_max_populate_servers        integer     1
inmemory_query                       string      ENABLE
inmemory_size                        big integer 400M
inmemory_trickle_repopulate_servers_ integer     1
optimizer_inmemory_aware             boolean     TRUE

SQL> alter session set container=pdb1;

Session altered.

SQL> alter database open;

Database altered.

SQL> show parameter inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_max_populate_servers        integer     1
inmemory_query                       string      ENABLE
inmemory_size                        big integer 400M
inmemory_trickle_repopulate_servers_ integer     1
optimizer_inmemory_aware             boolean     TRUE

SQL> alter system set inmemory_size=100M;

System altered.

SQL> show parameter inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_max_populate_servers        integer     1
inmemory_query                       string      ENABLE
inmemory_size                        big integer 100M
inmemory_trickle_repopulate_servers_ integer     1
optimizer_inmemory_aware             boolean     TRUE

这里可以发现inmemory_query默认为true,但是inmemory_size默认为0,也就是说In-Memory Option默认是关闭的,如果启用直接设置inmemory_size值即可(该值最小值为100M),但是需要注意在cdb中需要重启后生效,pdb需要待cdb生效后才能够设置

估算表设置In-Memory默认需要内存空间

SQL> create user chf identified by xifenfei;

User created.

SQL> grant dba to chf;

Grant succeeded.

SQL> create table chf.t_xifenfei as select * from dba_objects;

Table created.

SQL> select sum(bytes), sum(blocks) from DBA_segments where segment_name = 'T_XIFENFEI';

SUM(BYTES) SUM(BLOCKS)
---------- -----------
  13631488        1664

SQL> set serveroutput on
DECLARE
l_blkcnt_cmp binary_integer;
l_blkcnt_uncmp binary_integer;
l_row_cmp binary_integer;
l_row_uncmp binary_integer;
l_cmp_ratio number;
SQL>   2    3    4    5    6    7  l_comptype_str varchar2(100);
  8  BEGIN
  9  dbms_compression.get_compression_ratio(
 10  scratchtbsname => upper('&ScratchTBS'),
 11  ownname => upper('&ownername'), 
 12  objname => upper('&TableName'), 
 13  subobjname => NULL, 
 14  comptype => DBMS_COMPRESSION.COMP_INMEMORY_QUERY_LOW, 
 15  blkcnt_cmp => l_blkcnt_cmp,
 16  blkcnt_uncmp => l_blkcnt_uncmp, 
 17  row_cmp => l_row_cmp,
 18  row_uncmp => l_row_uncmp,
 19  cmp_ratio => l_cmp_ratio, 
 20  comptype_str => l_comptype_str 
 21  );
 22  dbms_output.put_line('.');
 23  dbms_output.put_line('OUTPUT: ');
 24  dbms_output.put_line('LINEORDER '||l_comptype_str||' ratio: '||to_char(l_cmp_ratio,'99.999'));
 25  end;
 26  /
Enter value for scratchtbs: USERS
old  10: scratchtbsname => upper('&ScratchTBS'),
new  10: scratchtbsname => upper('USERS'),
Enter value for ownername: CHF
old  11: ownname => upper('&ownername'),
new  11: ownname => upper('CHF'),
Enter value for tablename: T_XIFENFEI
old  12: objname => upper('&TableName'),
new  12: objname => upper('T_XIFENFEI'),
.
OUTPUT:
LINEORDER "In-memory Memcompress Query Low" ratio:   2.800

PL/SQL procedure successfully completed.

SQL> SELECT 13631488/2.800 FROM DUAL;

13631488/2.800
--------------
    4868388.57

SQL> alter table CHF.T_XIFENFEI inmemory;

Table altered.


SQL> select COUNT(*) FROM CHF.T_XIFENFEI;

  COUNT(*)
----------
     90923

SQL> select inmemory_size from v$im_segments where segment_name = 'T_XIFENFEI';

INMEMORY_SIZE
-------------
      4325376

SQL> select (4868388.57-4325376)/4325376 from dual;

(4868388.57-4325376)/4325376
----------------------------
                  .125541125

这里使用大家在ehcc中熟悉的dbms_compression.get_compression_ratio来估算In-memory需要的大概空间,例如本测试中,创建T_XIFENFEI表占用磁盘空间为13631488byte,使用dbms_compression估算在In-memory默认的压缩比例(Query Low)情况下,大概压缩比例为2.8,也就是通过合理估算,表启用In-memory cache之后,大概需要空间为13631488/2.800=4868388.57byte,最终通过实际测试需要空间为4325376byte,整体误差为(4868388.57-4325376)/4325376=12.5%左右
因此我们在使用In-memory cache一个表之时,如果不确定其需要内存大小,可以通过dbms_compression包来估算.另外In-memory还可以配置不同的压缩级别实现不同的压缩比例,其他压缩比例请见下图
compress-in_memory-1
compress-in_memory-2
详细link请见:https://docs.oracle.com/database/121/ARPLS/d_compress.htm#ARPLS65599

发表在 ORACLE 12C | 标签为 , | 一条评论

ORACLE 12C In-Memory功能性能测试

发表于 2014 年 4 月 25 日 由 惜分飞

启用In-Memory功能
数据库版本12.1.0.2及其以上版本,inmemory_size参数设置为合适值

SQL> SELECT * FROM V$VERSION;

BANNER                                                                               CON_ID
-------------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit                         0
PL/SQL Release 12.1.0.2.0 -                                                               0
CORE    12.1.0.2.0                                                                        0
TNS for Linux: Version 12.1.0.2.0 -                                                       0
NLSRTL Version 12.1.0.2.0 -                                                               0

SQL> SHOW PARAMETER inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_query                       string      ENABLE
inmemory_size                        big integer 200M

创建表
这里可以知道,创建表大小为13631488，但是未使用In-Memory功能

SQL> create table t_xifenfei_in_memory as select * from dba_objects;

Table created.

SQL> SELECT BYTES FROM USER_SEGMENTS WHERE SEGMENT_NAME='T_XIFENFEI_IN_MEMORY';

     BYTES
----------
  13631488

SQL> select TABLE_NAME,INMEMORY_PRIORITY,INMEMORY_DISTRIBUTE,INMEMORY_COMPRESSION from user_tables;

TABLE_NAME                     INMEMORY INMEMORY_DISTRI INMEMORY_COMPRESS
------------------------------ -------- --------------- -----------------
T_XIFENFEI_IN_MEMORY

SQL>  SELECT * FROM V$INMEMORY_AREA;

POOL                       ALLOC_BYTES USED_BYTES POPULATE_STATUS                CON_ID
-------------------------- ----------- ---------- -------------------------- ----------
1MB POOL                     166723584          0 DONE                                3
64KB POOL                     33554432          0 DONE                                3

未使用In-Memory功能测试

SQL> SET AUTOT TRACE
SQL> SELECT * FROM T_XIFENFEI_IN_MEMORY;

90902 rows selected.


Execution Plan
----------------------------------------------------------
Plan hash value: 3598036702

------------------------------------------------------------------------------------------
| Id  | Operation         | Name                 | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |                      | 90902 |     9M|   427   (1)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| T_XIFENFEI_IN_MEMORY | 90902 |     9M|   427   (1)| 00:00:01 |
------------------------------------------------------------------------------------------


Statistics
----------------------------------------------------------
          5  recursive calls
          0  db block gets
       7505  consistent gets
       1527  physical reads
          0  redo size
   12125231  bytes sent via SQL*Net to client
      67212  bytes received via SQL*Net from client
       6062  SQL*Net roundtrips to/from client
          2  sorts (memory)
          0  sorts (disk)
      90902  rows processed

这里可以看到未使用In-Memory功能,数据库查询执行计划使用TABLE ACCESS FULL，consistent gets为7505

使用In-Memory功能测试

SQL>  alter table  T_XIFENFEI_IN_MEMORY inmemory;

Table altered.

SQL> select TABLE_NAME,INMEMORY_PRIORITY,INMEMORY_DISTRIBUTE,INMEMORY_COMPRESSION from user_tables;

TABLE_NAME                     INMEMORY INMEMORY_DISTRI INMEMORY_COMPRESS
------------------------------ -------- --------------- -----------------
T_XIFENFEI_IN_MEMORY           NONE     AUTO DISTRIBUTE FOR QUERY

--因为只是把该表设置了INMEMORY,但是未查询过,所以查询V$INMEMORY_AREA中未使用相关内存
SQL> SELECT * FROM V$INMEMORY_AREA;

POOL                       ALLOC_BYTES USED_BYTES POPULATE_STATUS                CON_ID
-------------------------- ----------- ---------- -------------------------- ----------
1MB POOL                     166723584          0 DONE                                3
64KB POOL                     33554432          0 DONE                                3

--进行一次全表扫描
SQL> SELECT COUNT(*) FROM T_XIFENFEI_IN_MEMORY;

  COUNT(*)
----------
     90902

--再次查看，已经使用了分配的In-Memory中内存
SQL> SELECT * FROM V$INMEMORY_AREA;

POOL                       ALLOC_BYTES USED_BYTES POPULATE_STATUS                CON_ID
-------------------------- ----------- ---------- -------------------------- ----------
1MB POOL                     166723584    4194304 DONE                                3
64KB POOL                     33554432     131072 DONE                                3

SQL> SET AUTOT TRACE
SQL> SELECT * FROM T_XIFENFEI_IN_MEMORY;

90902 rows selected.

Execution Plan
----------------------------------------------------------
Plan hash value: 3598036702

---------------------------------------------------------------------------------------------------
| Id  | Operation                  | Name                 | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT           |                      | 90902 |     9M|    20  (45)| 00:00:01 |
|   1 |  TABLE ACCESS INMEMORY FULL| T_XIFENFEI_IN_MEMORY | 90902 |     9M|    20  (45)| 00:00:01 |
---------------------------------------------------------------------------------------------------


Statistics
----------------------------------------------------------
          3  recursive calls
          0  db block gets
          4  consistent gets
          0  physical reads
          0  redo size
    4946298  bytes sent via SQL*Net to client
      67212  bytes received via SQL*Net from client
       6062  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
      90902  rows processed

这里我们可以发现，使用了In-Memory功能之后，数据库consistent gets为4,相比未使用In-Memory之前的7505,性能最少提高近2000倍.

发表在 ORACLE 12C | 标签为 , | 评论关闭

ORACLE 12C In-Memory组件初试

发表于 2014 年 4 月 24 日 由 惜分飞

根据Oracle官方的宣传12.1.0.2的In-Memory组件实现内存列存储提高Oracle性能而且弥补在列存储中的不足。感谢Lunar的文档支持
12.1.0.2版本

[oracle@localhost ~]$ sqlplus chf/xifenfei@pdb1

SQL*Plus: Release 12.1.0.2.0 Beta on Thu Apr 24 21:39:43 2014

Copyright (c) 1982, 2014, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit     
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL> select * from v$version;

BANNER                                                                               CON_ID
-------------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit                         0
PL/SQL Release 12.1.0.2.0 -                                                               0
CORE    12.1.0.2.0                                                                        0
TNS for Linux: Version 12.1.0.2.0 -                                                       0
NLSRTL Version 12.1.0.2.0 -                                                               0

关于In-Memory组件

SQL>  select parameter,value from v$option where parameter like 'In-Memory%';

PARAMETER                                                        VALUE
---------------------------------------------------------------- -------------
In-Memory Column Store                                           TRUE
In-Memory Aggregation                                            TRUE

关于inmemory参数

SQL> select NAME,value,DESCRIPTION from v$parameter where NAME like 'inmemory%';

NAME                 VALUE
-------------------- --------------------
DESCRIPTION
---------------------------------------------------
inmemory_size        0
size in bytes of in-memory area

inmemory_clause_defa
ult
Default in-memory clause for new tables

inmemory_force       DEFAULT
Force tables to be in-memory or not

inmemory_query       ENABLE
Specifies whether in-memory queries are allowed

启用In-Memory功能

SQL> show parameter inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_query                       string      ENABLE
inmemory_size                        big integer 0

SQL> alter system set inmemory_size=200M scope=spfile;

System altered.

SQL> shutdown immediate
Pluggable Database closed.
SQL> startup
Pluggable Database opened.
SQL> show parameter inmemory;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ----------------------
inmemory_clause_default              string
inmemory_force                       string      DEFAULT
inmemory_query                       string      ENABLE
inmemory_size                        big integer 200M

创建测试表

SQL> create table t_xifenfei_in_memory as select * from dba_objects;

Table created.

SQL> select TABLE_NAME,INMEMORY_PRIORITY,INMEMORY_DISTRIBUTE,INMEMORY_COMPRESSION from user_tables;

TABLE_NAME                     INMEMORY INMEMORY_DISTRI INMEMORY_COMPRESS
------------------------------ -------- --------------- -----------------
T_XIFENFEI_IN_MEMORY

SQL> alter table  T_XIFENFEI_IN_MEMORY inmemory;

Table altered.

SQL> select TABLE_NAME,INMEMORY_PRIORITY,INMEMORY_DISTRIBUTE,INMEMORY_COMPRESSION from user_tables;

TABLE_NAME                INMEMORY INMEMORY_DISTRI INMEMORY_COMPRESS
------------------------- -------- --------------- -----------------
T_XIFENFEI_IN_MEMORY      NONE     AUTO DISTRIBUTE FOR QUERY
发表在 ORACLE 12C | 标签为 , | 3 条评论