Oracle限制

 

Author：skate

Time：2009-03-05

昨天和一个朋友聊天，谈到oracle的限制，有点模糊了，于是今天仔细查下，记录在这

oracle 9i表空间的数据文件个数上限是 1022个，系统默认是200个，通过参数db_files来控制

但数据库总共有65533个数据文件，这就看表空间个数和数据文件个数你自己做个选择了

测试如下：

SQL> show parameter db_files;

NAME                                 TYPE

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

VALUE

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

db_files                             integer

205

SQL> alter system set db_files=2000 scope=spfile;

系统已更改。

SQL> alter system set db_files=4000 scope=spfile;

系统已更改。

这么大也可以啊

SQL> alter system set db_files=10000 scope=spfile;

系统已更改。

SQL> alter system set db_files=100000000 scope=spfile;

系统已更改。

还可以，难道就没有限制吗：继续....

SQL> alter system set db_files=100000000000 scope=spfile;

alter system set db_files=100000000000 scope=spfile

                          *

ERROR 位于第 1 行:

ORA-02017: 要求整数值

终于报错了，查了下整数的范围是[-2^31, 2^31-1]。即[-2147483648, 2147483647]。

SQL> alter system set db_files=10000000000 scope=spfile;

alter system set db_files=10000000000 scope=spfile

                          *

ERROR 位于第 1 行:

ORA-02017: 要求整数值

 

SQL> alter system set db_files=1000000000 scope=spfile;

系统已更改。

SQL> alter system set db_files=2000000000 scope=spfile;

系统已更改。

SQL> alter system set db_files=3000000000 scope=spfile;

alter system set db_files=3000000000 scope=spfile

*

ERROR 位于第 1 行:

ORA-00600: 内部错误代码，参数: [925], [db_files], [-1294967296], [], [], [],

[], []

 

SQL> alter system set db_files=2000000000 scope=spfile;

系统已更改。

需要重启数据库，才能生效，即：recreate controlfile

 

关闭数据库

 

SQL> shutdown immediate;

数据库已经关闭。

已经卸载数据库。

ORACLE 例程已经关闭。

SQL> startup

ORA-01131: DB_FILES system parameter value 2000000000 exceeds limit of 65534

 

从这里可以得到两个信息：

1. 对于alter system ， oracle不验证其值的有效性

2. 得到了数据文件个数的最大值

 

结果数据无法启动了

我用pfile启动数据库

SQL> startup pfile='C:/oracle/admin/ora9i/pfile/init.ora.98200816645'

ORACLE 例程已经启动。

Total System Global Area  135338868 bytes

Fixed Size                   453492 bytes

Variable Size             109051904 bytes

Database Buffers           25165824 bytes

Redo Buffers                 667648 bytes

数据库装载完毕。

数据库已经打开。

SQL> create spfile from pfile;

create spfile from pfile

*

ERROR 位于第 1 行:

ORA-01078: 处理系统参数失败

LRM-00109: could not open parameter file

'C:/ORACLE/PRODUCT/9.2.0.1/DB_1/DATABASE/INITORA9I.ORA'

 

SQL> create spfile from pfile;

create spfile from pfile

*

ERROR 位于第 1 行:

ORA-01078: 处理系统参数失败

LRM-00109: could not open parameter file

'C:/ORACLE/PRODUCT/9.2.0.1/DB_1/DATABASE/INITORA9I.ORA'

 

SQL> create spfile from pfile='C:/oracle/admin/ora9i/pfile/init.ora.98200816645';

文件已创建。

SQL> alter system set db_files=65534 scope=spfile;

系统已更改。

SQL> show parameter db_files

NAME                                 TYPE

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

VALUE

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

db_files                             integer

200

SQL> shutdown immediate;

数据库已经关闭。

已经卸载数据库。

ORACLE 例程已经关闭。

SQL> startup

ORACLE 例程已经启动。

Total System Global Area  579935836 bytes

Fixed Size                   454236 bytes

Variable Size             553648128 bytes

Database Buffers           25165824 bytes

Redo Buffers                 667648 bytes

数据库装载完毕。

数据库已经打开。

SQL> show parameter db_files;

NAME                                 TYPE

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

VALUE

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

db_files                             integer

65534

SQL>

A Database Limits

This appendix lists the limits of values associated with database functions and objects. Limits exist on several levels in the database. There is usually a hard-coded limit in the database that cannot be exceeded. This value may be further restricted for any given operating system.

Database limits are divided into four categories:

·         Datatype Limits

·         Physical Database Limits

·         Logical Database Limits

·         Process and Runtime Limits

 

http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/limits.htm#REFRN004

 

Datatype Limits

Datatypes	Limit	Comments
BFILE	Maximum size: 4 GB Maximum size of a file name: 255 characters Maximum size of a directory name: 30 characters Maximum number of open BFILEs: see Comments	The maximum number of BFILEs is limited by the value of the SESSION_MAX_OPEN_FILES initialization parameter, which is itself limited by the maximum number of open files the operating system will allow.
BLOB	Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Foot 1 ).
CHAR	Maximum size: 2000 bytes
CHAR VARYING	Maximum size: 4000 bytes
CLOB	Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Footref 1).
Literals (characters or numbers in SQL or PL/SQL)	Maximum size: 4000 characters
LONG	Maximum size: 2 GB - 1	Only one LONG column is allowed per table.
NCHAR	Maximum size: 2000 bytes
NCHAR VARYING	Maximum size: 4000 bytes
NCLOB	Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Footref 1).
NUMBER	999...(38 9's) x10125 maximum value	Can be represented to full 38-digit precision (the mantissa).
	-999...(38 9's) x10125 minimum value	Can be represented to full 38-digit precision (the mantissa).
Precision	38 significant digits
RAW	Maximum size: 2000 bytes
VARCHAR	Maximum size: 4000 bytes
VARCHAR2	Maximum size: 4000 bytes

 

 

 

Physical Database Limits

Item	Type of Limit	Limit Value
Database Block Size	Minimum	2048 bytes; must be a multiple of operating system physical block size
	Maximum	Operating system dependent; never more than 32 KB
Database Blocks	Minimum in initial extent of a segment.	2 blocks
	Maximum per datafile	Platform dependent; typically 222 - 1 blocks
Controlfiles	Number of control files	1 minimum; 2 or more (on separate devices) strongly recommended
	Size of a control file	Dependent on operating system and database creation options; maximum of 20,000 x (database block size)
Database files	Maximum per tablespace	Operating system dependent; usually 1022
	Maximum per database	65533 May be less on some operating systems Limited also by size of database blocks and by the DB_FILES initialization parameter for a particular instance
Database extents	Maximum per dictionary managed tablespace	4 GB * physical block size (with K/M modifier); 4 GB (without K/M modifier)
	Maximum per locally managed (uniform) tablespace	2 GB * physical block size (with K/M modifier); 2 GB (without K/M modifier)
Database file size	Maximum	Operating system dependent. Limited by maximum operating system file size; typically 222 or 4 MB blocks
MAXEXTENTS	Default value	Derived from tablespace default storage or DB_BLOCK_SIZE initialization parameter
	Maximum	Unlimited
Redo Log Files	Maximum number of logfiles	Limited by value of MAXLOGFILES parameter in the CREATE DATABASE statement Control file can be resized to allow more entries; ultimately an operating system limit
	Maximum number of logfiles per group	Unlimited
Redo Log File Size	Minimum size	50 KB
	Maximum size	Operating system limit; typically 2 GB
Tablespaces	Maximum number per database	64 K Number of tablespaces cannot exceed the number of database files because each tablespace must include at least one file
Bigfile Tablespaces	Number of blocks	A bigfile tablespace contains only one datafile or tempfile, which can contain up to approximately 4 billion ( 232 ) blocks. The maximum size of the single datafile or tempfile is 128 terabytes (TB) for a tablespace with 32K blocks and 32TB for a tablespace with 8K blocks.
Smallfile (traditional) Tablespaces	Number of blocks	A smallfile tablespace is a traditional Oracle tablespace, which can contain 1022 datafiles or tempfiles, each of which can contain up to approximately 4 million (222) blocks.
External Tables file	Maximum size	Dependent on the operating system. An external table can be composed of multiple files.

 

 

 

Logical Database Limits

Item	Type	Limit
CREATE MATERIALIZED VIEW definition	Maximum size	64K Bytes
GROUP BY clause	Maximum length	The GROUP BY expression and all of the nondistinct aggregate functions (for example, SUM, AVG) must fit within a single database block.
Indexes	Maximum per table	Unlimited
	total size of indexed column	75% of the database block size minus some overhead
Columns	Per table	1000 columns maximum
	Per index (or clustered index)	32 columns maximum
	Per bitmapped index	30 columns maximum
Constraints	Maximum per column	Unlimited
Subqueries	Maximum levels of subqueries in a SQL statement	Unlimited in the FROM clause of the top-level query 255 subqueries in the WHERE clause
Partitions	Maximum length of linear partitioning key	4 KB - overhead
	Maximum number of columns in partition key	16 columns
	Maximum number of partitions allowed per table or index	1024K - 1
Rows	Maximum number per table	Unlimited
Stored Packages	Maximum size	PL/SQL and Developer/2000 may have limits on the size of stored procedures they can call. The limits typically range from 2000 to 3000 lines of code. See Also: Your PL/SQL or Developer/2000 documentation for details
Trigger Cascade Limit	Maximum value	Operating system-dependent, typically 32
Users and Roles	Maximum	2,147,483,638
Tables	Maximum per clustered table	32 tables
	Maximum per database	Unlimited

 

 

Process and Runtime Limits

Item	Type	Limit
Instances per database	Maximum number of cluster database instances per database	Operating system-dependent
Locks	Row-level	Unlimited
	Distributed Lock Manager	Operating system dependent
SGA size	Maximum value	Operating system-dependent; typically 2 to 4 GB for 32-bit operating systems, and > 4 GB for 64-bit operating systems
Advanced Queuing Processes	Maximum per instance	10
Job Queue Processes	Maximum per instance	1000
I/O Slave Processes	Maximum per background process (DBWR, LGWR, etc.)	15
	Maximum per Backup session	15
Sessions	Maximum per instance	32 KB; limited by the PROCESSES and SESSIONS initialization parameters
Global Cache Service Processes	Maximum per instance	10
Shared Servers	Maximum per instance	Unlimited within constraints set by the PROCESSES and SESSIONS initialization parameters, for instance
Dispatchers	Maximum per instance	Unlimited within constraints set by PROCESSES and SESSIONS initialization parameters, for instance
Parallel Execution Slaves	Maximum per instance	Unlimited within constraints set by PROCESSES and SESSIONS initialization parameters, for instance
Backup Sessions	Maximum per instance	Unlimited within constraints set by PROCESSES and SESSIONS initialization parameters, for instance

 

 

Oracle中数据文件大小的限制

Oracle数据文件的大小存在一个内部限制，这个限制是：
每个数据文件最多只能包含2^22-1个数据块。

这个限制也就直接导致了每个数据文件的最大允许大小。
在2K Block_size下，数据文件最大只能达到约8G
在32K的Block_size下，数据文件最大只能达到约16*8G的大小。

这个限制是由于Oracle的Rowid中使用22位来代表Block号，这22位最多只能代表2^22-1个数据块。

为了扩展数据文件的大小，Oracle10g中引入了大文件表空间，在大文件表空间下，Oracle使用32位来代表Block号，也就是说，在新的技术下，大文件表空间下每个文件最多可以容纳4G个Block。
那么也就是说当Block_size为2k时，数据文件可以达到8T 。
当block_size为32K时，数据文件可以达到128T。

上周在做2K block_size测试时，第一次遇到了这个限制：

SQL> alter tablespace eygle add datafile 'f:/eygle02.dbf' size 8192M;
alter tablespace eygle add datafile 'f:/eygle02.dbf' size 8192M
*
ERROR 位于第 1 行:
ORA-01144: 文件大小 (4194304 块) 超出 4194303 块的最大数

缩减一点，最后创建成功：

SQL> alter tablespace eygle add datafile 'f:/eygle02.dbf' size 8191M reuse;

表空间已更改。

已用时间: 00: 44: 42.08

 

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