Physical Database Limits

Item Type of Limit Limit ValueDatabase Block Size Minimum 2048 bytes;

must be a multiple of operating systemphysical block size

Maximum Operating system dependent;never more than 32 KB

Database Blocks Minimum in initial 2 blocksextent ofa segment.

Maximum per datafile Platform dependent;typically 222-1 blocks

Controlfiles Number of control files 1 minimum; 2 or more (on separate devices) stronglyrecommended

Size of a control file Dependent on operating system and database creationoptions; maximum of 20,000 x (database block size)

Database files Maximum per tablespace Operating system dependent; usually 1022Maximum per database 65533

May be less on some operating systemsLimited also by size of database blocks and by the DB_FILES initialization parameter for a particular instance.

Database extents Maximum 2 GB, regardless of the maximum file size allowed bythe operating system

Database file size Maximum Operating system dependent. Limited by maximumoperating system file size; typically 222 or 4M Blocks.

MAXEXTENTS Default value Derived from tablespace default storage or DB_BLOCK_

SIZE initialization parameterMaximum Unlimited

Redo Log Files Maximum number of Limited by value of LOG_FILES initialization parameterlogfiles or MAXLOGFILES parameter in the CREATE DATABASE

statement

Control file can be resized to allow more entries;ultimately an operating system limit

Maximum number of Unlimitedlogfiles per group

Redo Log File Size Minimum size 50 KBMaximum size Operating system limit; typically 2 GB

Tablespaces Maximum number per 64 Kdatabase Number of tablespaces cannot exceed the number of

database files, as each tablespace must include at leastone file

Logical Database Limits

Item Type of Limit Limit ValueGROUP BY clause Maximum length The GROUP BY expression and all of the

nondistinct aggregates functions (for example,SUM, AVG) must fit within a single databaseblock.

Indexes Maximum per table Unlimitedtotal size of indexed column 75% of the database block size minus some

overhead

Columns Per table 1000 columns maximumPer index (or clustered index) 32 columns maximum

Per bitmapped index 30 columns maximum

Constraints Maximum per column UnlimitedSubqueries Maximum levels of subqueries Unlimited in the FROM clause of the top-level

in a SQL statement query query255 subqueries in the WHERE clause

Partitions Maximum length of linear 4 KB - overheadpartitioning key

Maximum number of columns 16 columnsin partition key

Maximum number of partitions 64 K-1 partitionsallowed per table or index

Rollback Segments Maximum number per database No limit; limited within a session by the MAX_ROLLBACK_SEGMENTS initialization parameter

Rows Maximum number per table Unlimited

SQL Statement Length Maximum length of statements 64 K maximum; particular tools may imposelower limits

Stored Packages Maximum size PL/SQL and Developer/2000 may have limitson the size of stored procedures they can callThe limits typically range from 2000 to 3000lines of code.See Also: Your PL/SQL or Developer/2000documentation for details

Trigger Cascade Limit Maximum value Operating system-dependent, typically 32

Users and Roles Maximum 2,147,483,638

Tables Maximum per clustered tabls 32 tablesMaximum per database Unlimited

Process and Runtime Limits

Item Type of Limit Limit ValueInstances per database Maximum number of OPS Operating system-dependent

instances per database

Locks Row-level Unlimited

Distributed Lock Manag er Operating system dependent

SGA size Maximum value Operating system-dependent; typically 2 to 4GB for 32-bit operating systems, and > 4 GBfor 64-bit operating systems

Advanced Queuing Maximum per instance 10Processes

Job Queue Processes Maximum per instance 1000

I/O Slave Processes Maximum per background 15process (DBWR, LGWR, etc)

Maximum per Backup session 15

Sessions Maximum per instance 32K; limited by thePROCESSESandSESSIONSinitialization parameters

LCK Processes Maximum per instance 10

Shared Servers Maximum per instance Unlimited within constraints set by thePROCESSES and SESSIONS initializationparameters, for instance

Dispatchers Maximum per instance Unlimited within constraints set byPROCESSESand SESSIONS initialization parameters, forinstance

Parallel Maximum per instance Unlimited within constraints set byPROCESSESExecution Slaves and SESSIONS initialization parameters, for

instance

Backup Sessions Maximum per instance Unlimited within constraints set byPROCESSESand SESSIONS initialization parameters, forinstance

Logical Database Limits

Item Type of LimitGROUP BY clause Maximum length

Indexes Maximum per tabletotal size of indexed column

Columns Per tablePer index (or clustered index)Per bitmapped index

Constraints Maximum per columnSubqueries Maximum levels of subqueries

in a SQL statement query

Partitions Maximum length of linearpartitioning key

Maximum number of columnsin partition key

Maximum number of partitionsallowed per table or index

Rollback Segments Maximum number per database

Rows Maximum number per table

SQL Statement Length Maximum length of statements

Stored Packages Maximum size

Trigger Cascade Limit Maximum value

Users and Roles Maximum

Tables Maximum per clustered tabls

Maximum per database

Limit ValueThe GROUP BY expression and all of thenondistinct aggregates functions (for example,SUM, AVG) must fit within a single databaseblock.

Unlimited75% of the database block size minus someoverhead

1000 columns maximum32 columns maximum30 columns maximum

UnlimitedUnlimited in the FROM clause of the top-levelquery255 subqueries in the WHERE clause

4 KB - overhead

16 columns

64 K-1 partitions

No limit; limited within a session by the MAX_ROLLBACK_SEGMENTS initialization parameter

Unlimited

64 K maximum; particular tools may imposelower limits

PL/SQL and Developer/2000 may have limitson the size of stored procedures they can callThe limits typically range from 2000 to 3000lines of code.See Also: Your PL/SQL or Developer/2000documentation for details

Operating system-dependent, typically 32

2,147,483,638

32 tables

Unlimited

Process and Runtime Limits

Item Type of LimitInstances per database Maximum number of OPS

instances per database

Locks Row-level

Distributed Lock Manag

SGA size Maximum value

Advanced Queuing Maximum per instanceProcesses

Job Queue Processes Maximum per instance

I/O Slave Processes Maximum per backgroundprocess (DBWR, LGWR, etc)

Maximum per Backup session

Sessions Maximum per instance

LCK Processes Maximum per instance

Shared Servers Maximum per instance

Dispatchers Maximum per instance

Parallel Maximum per instanceExecution Slaves

Backup Sessions Maximum per instance

Limit ValueOperating system-dependent

Unlimited

er Operating system dependent

Operating system-dependent; typically 2 to 4GB for 32-bit operating systems, and > 4 GBfor 64-bit operating systems

10

1000

15

15

32K; limited by thePROCESSESandSESSIONSinitialization parameters

10

Unlimited within constraints set by thePROCESSES and SESSIONS initializationparameters, for instance

Unlimited within constraints set byPROCESSESand SESSIONS initialization parameters, forinstance

Unlimited within constraints set byPROCESSESand SESSIONS initialization parameters, forinstance

Unlimited within constraints set byPROCESSESand SESSIONS initialization parameters, forinstance