ORACLE数据库的限制

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.

Item

Type

Limit

CREATE MATERIALIZED VIEWdefinition

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