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NonStop SQL/MP Reference Manual

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Table Of Contents
NonStop SQL/MP Reference Manual—142115
L-8
Limits
The maximum number of tables that can be specified in a FROM clause is 16. This
maximum includes the underlying base tables of views.
•
IN predicate expressions
The maximum number of expressions in the expression-list of an IN
predicate is 500.
•
Index length
The maximum length depends on the index type:
The length of any column that allows null values is 2 bytes longer than the declared
length of the column.
•
Indexes per table
The maximum number of indexes depends on the number of columns in the key, the
number of partitions in each index, and additional factors. If there are no partitions
in the indexes, a table can have a maximum of from 60 to 120 indexes; in some
situations, however, as few as 32 indexes are allowed. If there are 25 partitions per
index and there is a total of 10 columns in the primary key and index, the maximum
number of indexes in a table could be reduced to as few as 34 (for a table with
standard partition arrays) or 66 (for a key-sequenced table with extended partition
arrays).
Additional factors that affect the index limit are the number of columns in the index,
the number of indexes for the underlying table, the number of protection views
defined for the underlying table, and the number of catalogs used to describe the
indexes. The description of all of the indexes for a table must fit in a file label.
•
Lock limit
SQL defines a lock limit for the number of row locks that a program can own. The
limit is internal to NonStop SQL/MP software. If a program exceeds the limit and
the locks cannot be upgraded to table locks, the program receives an error message.
•
MAXEXTENTS
The maximum number of extents allowed is 959 per file or primary partition and
940 for a secondary partition. This number is decreased if the extent size (primary or
secondary) is very large, such as a secondary extent size of 2,000 pages.
•
Partition size
The maximum partition size that NonStop SQL/MP software can support is
approximately 2.1465 gigabytes. This number is determined by the following
formula: 2**31 - 1 - 1 megabyte. The 1 megabyte of space is for internal use.
Unique The sum of the length of the columns in the index cannot exceed 253
bytes.
Nonunique The sum of the length of the columns in the index plus the sum of the
key of the underlying table cannot exceed 253 bytes.