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.

以上表格引用:
download.oracle.com/docs/cd/B19306_01/server.102/b14237/limits002.htm#sthref4183

ROWID:
ROWID的结构如下面的例子:(6,3,6,3)

Examples of Rowid Use

You can use the function SUBSTR to break the data in a rowid into its components. For example, you can use SUBSTR to break an extended rowid into its four components (database object, file, block, and row):

SELECT ROWID, 
       SUBSTR(ROWID,1,6) "OBJECT", 
       SUBSTR(ROWID,7,3) "FIL", 
       SUBSTR(ROWID,10,6) "BLOCK", 
       SUBSTR(ROWID,16,3) "ROW" 
       FROM products; 

ROWID               OBJECT  FIL  BLOCK   ROW 
------------------  ------  ---  ------  ---- 
AAAA8mAALAAAAQkAAA  AAAA8m  AAL  AAAAQk  AAA 
AAAA8mAALAAAAQkAAF  AAAA8m  AAL  AAAAQk  AAF 
AAAA8mAALAAAAQkAAI  AAAA8m  AAL  AAAAQk  AAI 

SMALLFILE:
rowid中的FIL使用3bytes, block#使用6bytes是属于smallfile的情况,是数据库的缺省数据文件类型
这样oracle可以支持的单个文件的块数是2^22 -> 4M blocks
当1个block为8k缺省大小时,单个数据文件大小为32GB.

SQL>select * from database_properties where property_name = 'DEFAULT_TBS_TYPE';

可以通过以下方式查询数据库中数据文件类型:
SQL>select file_name,file_id,relative_fno from dba_data_files;

改变缺省数据文件类型:
SQL>ALTER DATABASE SET DEFAULT bigfile TABLESPACE;

BIGFILE:
当BIGFILE数据文件类型时,每个标空间只能存在1个文件.这样在rowid中的FIL可以取消,
而block#可以使用额外的3bytes原FIL数据位共9bytes的容量来存放文件.
这样oracle可以支持文件块数为2^32 -> 4G blocks
当1个block为8k缺省大小时,该数据文件的大小为32TB.

各种数据文件的极限大小由数据库平台所支持的文件大小所决定.