SQL/MX 2.x Reference Manual (H06.04+)

HP NonStop SQL/MX Reference Manual—540440-003
C-1
C Limits
This appendix lists limits for various parts of NonStop SQL/MX:
Catalog names 128 characters in length.
Column names 128 characters in length.
Constraints The maximum combined length of the columns for a
REFERENCE, PRIMARY KEY, or UNIQUE constraint is
255 bytes.
DROP SCHEMA
CASCADE transactions
You might need to increase the number of locks per
volume, or DROP SCHEMA CASCADE can fail.
EXTENTS Limited only by size of disk.
FROM clause of the
SELECT statement
NonStop SQL/MX typically generates good plans up to
16 tables and tries to generate plans with acceptable
performance for queries up to 40 tables. Beyond that
limit, the queries require some tuning to compile and
run.
IN predicate 1900 expressions are allowed.
Indexes The maximum combined length of the columns for an
index is 255 bytes. A nonunique index consists of
columns and a clustering key. A unique index consists
of columns only.
There is no restriction on the number of indexes per
table but creating many indexes on a table will affect
performance.
There are no restrictions on the number of partitions an
index supports, but beyond 512, performance and
memory issues may occur.
INSERT operations 150 records can be inserted into SQL/MX tables in a
single INSERT operation. 250 records can be inserted
into SQL/MP tables in a single INSERT operation.
Joins 40 tables can be joined, including base tables of views,
but joining more tables affects performance.
MAXEXTENTS size 768 (compare with 919 for NonStop SQL/MP)
Partitions There are no restrictions on the number of partitions an
table can support, but beyond 512, performance and
memory issues may occur.
Partitions can be on the same physical disk as the main
file (SQL/MP partitions must be on a different disk.)
PFS usage PFS usage is decreased in the file system. This issue
affects the number of opens.