For example, the maximum number of database files allowed by the Oracle7 Server can be reduced for a particular database by specifying a lower value for the MAXDATAFILES option of the CREATE DATABASE command. This limit is then recorded in the control file and cannot be exceeded for the life of that database. You can alter the value of the initialization parameter DB_FILES to a value less than MAXDATAFILES for a particular instance. The maximum number of database files is then limited to the number specified by DB_FILES for the life of that instance.
For more information on the maximum value of such limits, see your operating system-specific Oracle documentation.
Item
| Type
| Limit
|
blocks (Oracle7)
| minimum in initial extent
| 2 blocks (automatically enforced)
|
| maximum
| 232 -1 (up to 4 terabytes, depending on block size)
|
characters
| CHAR column index
| 255 characters maximum no absolute limit, but a function of block size LONG column 231 -1 characters (2 gigabytes) maximum VARCHAR2 column 2000 characters maximum
|
columns
LONG columns
| index (or cluster index)
table
expression list view definition
| 16 columns maximum
254 columns maximum
254 columns maximum
254 columns maximum
|
| table
| 1 LONG column per table
|
constraints
| CHECK (on columns)
| unlimited
|
context area
| size
| no absolute limit
(1024 is the minimum initial extent size)
|
control files
| number of control files
| one minimum: 2 or more strongly recommended on separate devices
|
| size of a control file
| typically 50..200Kb, depending on database creation options; maximum is O/S-dependent
|
database files
| system
| 1022 or value of DB_FILES in INIT.ORA, or limited by value of MAXDATAFILES in CREATE DATABASE. Less on some operating systems.
|
database file size
| minimum
| no absolute limit except for first file whose minimum size is 2 MB
|
| maximum
| O/S dependent, typically 16 million Oracle7 blocks
|
GROUP BY clause
| maximum size
| number of bytes limited to one Oracle7 block, less O/S-dependent block overhead, less 2-bytes per group-by expression, less one of the following:
2 bytes plus size of each aggregate
of a non-distinct value
Example:
COUNT(DISTINCT(x))
or
two bytes plus size in bytes of the
longest aggregate of a distinct value
Example: COUNT(x)
|
indexes
| table
| no limit
|
| total size of indexed columns
| one-half the Oracle7 block size minus some overhead
|
instances
| parallel server
| O/S dependent, subject to Oracle7 limit of 255
|
literals
| character string number (+ or -)
| 255 characters
(10E-135 to 10E125)
|
locks
| transaction distributed
| no limit; O/S dependent
|
MAXEXTENTS
|
| derived from DB_BLOCK_SIZE
O/S dependent
|
nested queries
|
| 255 queries
|
NUMBER
| maximum value
| 1.0x10125
|
precision
|
| up to 38 significant digits per numeric value
|
redo log files
| database
| 255 or value for LOG_FILES in INIT.ORA, or by MAXLOGFILES in CREATE DATABASE. Ultimately, an operating system limit.
|
redo log file size
| minimum
| 50 Kbytes
|
rollback segments
| database
| no limit
|
rows
| table
| no limit
|
SGA size
| maximum
| no limit
|
SQL statement length
|
| 64 K maximum length; particular tools may have lower limits
|
stored packages
| size
| SQL*FORMS may have limits on the size of stored procedures you can call. Consult your SQL*Forms documentation for details.
|
tablespaces
| database
| no limit
|
tables
| cluster database
| 32; no limit
|
trigger cascade limit
| maximum
| 32, larger values O/S-dependent
|
users and roles
| maximum
| 65525 (users and roles combined)
|