A.3 Logical Database Limits

This table describes limit types and limit values for logical database items.

Item	Type of Limit	Limit Value
Columns	Maximum per table	1000
Columns	Maximum per index (or clustered index)	32
Columns	Maximum per bitmapped index	30
Constraints	Maximum per column	Unlimited Oracle does not define a limit on the number of constraints per column. However, constraints are subject to the limit on the maximum number of constraints in the database. See the entry for "Constraints - Maximum per database" in this table.
Constraints	Maximum per database	4,294,967,293
Database users	Maximum per database	4,294,967,293
Dictionary-managed database objects	Maximum per database	4,254,950,911 - overhead
Indexes	Maximum per table	Unlimited Oracle does not define a limit on the number of indexes per table. However, indexes are subject to the limit on the maximum number of dictionary-managed database objects allowed per database. See the entry for "Dictionary-managed database objects" in this table.
Indexes	Total size of indexed column(s)	Approximately 75% of the database block size minus some overhead
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	Approximately 6,000,000 lines of code. See Also: Oracle Database PL/SQL Language Reference for details
Subpartitions	Maximum number of subpartitions in a composite partitioned table	1024K - 1
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
System Change Numbers (SCNs)	Maximum	263 - 248 = 9,223,090,561,878,065,152 SCNs
Tables	Maximum per clustered table	32 tables
Tables	Maximum per database	Unlimited Oracle does not define a limit on the number of tables per database. However, tables are subject to the limit on the maximum number of dictionary-managed database objects allowed per database. See the entry for "Dictionary-managed database objects" in this table.
Trigger Cascade Limit	Maximum value	Operating system-dependent, typically 32
Users and Roles	Maximum	2,147,483,638

Note:

The limit on how long a SQL statement can be depends on many factors, including database configuration, disk space, and memory

Note:

When an object instance exists in memory, there is no fixed limit on the number of attributes in the object. But the maximum total amount of memory consumed by an object instance is 4 GB. When an object instance is inserted into a table, the attributes are exploded into separate columns in the table, and the Oracle 1000-column limit applies.