Data Type 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, 1000). |
CHAR |
Maximum size: 2000 bytes | None |
CHAR VARYING |
Maximum size: 4000 bytes | None |
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, 1000). |
| Literals (characters or numbers in SQL or PL/SQL) | Maximum size: 4000 characters | None |
LONG |
Maximum size: 2 GB - 1 | Only one LONG column is allowed per table. |
NCHAR |
Maximum size: 2000 bytes | None |
NCHAR VARYING |
Maximum size: 4000 bytes | None |
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, 1000). |
NUMBER |
999...(38 9's) x10125 maximum value -999...(38 9's) x10125 minimum value | Can be represented to full 38-digit precision (the mantissa) Can be represented to full 38-digit precision (the mantissa) |
| Precision | 38 significant digits | None |
RAW |
Maximum size: 2000 bytes | None |
VARCHAR |
Maximum size: 4000 bytes | None |
VARCHAR2 |
Maximum size: 4000 bytes | None |
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Physical Database Limitation
| 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 222 - 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 20,000 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 222 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 ( 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. |
| 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. |
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Logical Database Limitation
| Item | Type of Limit | Limit Value |
|---|---|---|
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 |
| Indexes | Total size of indexed column | 75% of the database block size minus some overhead |
| Columns | Per table | 1000 columns maximum |
| Columns | Per index (or clustered index) | 32 columns maximum |
| Columns | 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 |
| Partitions | Maximum number of columns in partition key | 16 columns |
| Partitions | 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 |
| Tables | Maximum per database | Unlimited |
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Process and Runtime Limitation
| Item | Type of Limit | Limit Value |
|---|---|---|
| Instances per database | Maximum number of cluster database instances per database | Operating system-dependent |
| Locks | Row-level | Unlimited |
| Locks | 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 |
| I/O Slave Processes | 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 |
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