Oracle 数据文件 大小设置 说明
先看Oracle 官网的说明, 看的是Oracle 10gR2的文档：
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 |
| Database Block Size |
Maximum |
Operating system dependent; never more than 32 KB |
| Database Blocks |
Minimum in initial extent of a segment |
2 blocks |
| Database Blocks |
Maximum per datafile |
Platform dependent; typically 2^22 - 1 blocks |
| Controlfiles |
Number of control files |
1 minimum; 2 or more (on separate devices) strongly recommended |
| Controlfiles |
Size of a control file |
Dependent on operating system and database creation options; maximum of 25,000 x (database block size) |
| Database files |
Maximum per tablespace |
Operating system dependent; usually 1022 |
| Database files |
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) |
| Database extents |
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 2^22 or 4 MB blocks |
| MAXEXTENTS |
Default value |
Derived from tablespace default storage or DB_BLOCK_SIZE initialization parameter |
| MAXEXTENTS |
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 |
| Redo Log Files |
Maximum number of logfiles per group |
Unlimited |
| Redo Log File Size |
Minimum size |
4 MB |
| Redo Log File Size |
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 ( 2^32 ) blocks. The maximum size of the single datafile or tempfile is 128 terabytes (TB) for a tablespace with 32 K blocks and 32 TB for a tablespace with 8 K 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 (2^22) blocks. |
| External Tables file |
Maximum size |
Dependent on the operating system. An external table can be composed of multiple files. |
From：
http://download.oracle.com/docs/cd/E11882_01/server.112/e17110/limits002.htm#REFRN0042
每个数据文件最多只能包含2^22-1个数据块。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。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8K Block size 下， 数据文件最大只能达到约4*8G；
在32K Block size下，数据文件最大只能达到约16*8G。.
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 32 K blocks and 32 TB for a tablespace with 8 K blocks.
Bigfile tablespace 只允许一个数据文件,在大文件表空间下，Oracle使用32位来代表Block号， 每个文件最多可以容纳4G（2^32）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8k时，数据文件可以达到32T。 当block_size 为32K时，数据文件可以达到128T。
一般不建议把单个数据文件建的太大。 因为太大的话，如果某个数据文件出现问题，恢复起来费时较长。
一般都是把单个数据文件设成8G一个，如果表空间较大的话，可以多弄几个数据文件。 在上面的表格里也提到了。 单个表空间最大支持1022个数据文件。所以数据文件是绝对够用的。
至于为什么设置8G，不是清楚，以前问过同事，说是和EXT3 的文件系统有关系。 刚才在metalink上也搜了一下， 想找到相关的官方证据。搜了半天，没有搜到相关的理论支持。 不过单个数据文件8G 是很通用的设法。 以后找到相关理论支持在补充。
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