iX V6.5 (30391-90011)

Chapter 11 509

B-Tree Indices

Limits

These are some limits on the use of B-Tree indices:

• Key limits

KSAM limits keys up to 255 bytes. TurboIMAGE/XL limits keys to 510 bytes (255

halfwords). TurboIMAGE items are always an even number of bytes in length, with 2

bytes for internal use. This means that the maximum TurboIMAGE key that can be

indexed is 252 bytes. Attempting to build an index for a master data set whose key is

greater than 252 bytes will not succeed, and will generate an error message.

• Maximum number of ﬁle opens

MPE/iX currently limits a single process to opening a maximum of 1023 ﬁles at a time.

For a database with 199 sets, 100 of which are master data sets with B-Tree indices, if

all sets are open at the same time, an additional 100 ﬁles will be open.

• Pattern matching

The only types of generic key pattern matching supported are:

= search for item values equal to the speciﬁed value

< search for item values less than speciﬁed value

<= search for item values less than or equal to the speciﬁed value

> search for item values greater than speciﬁed value

>= search for item values greater than or equal to the speciﬁed value

[ ] search for item values between and including two speciﬁed values.

@c search for items with a common preﬁx.

PK search for items with partial key.

The operator < > for "not equal to" and the range search ( ) are not supported.