Communicator 3000 MPE/iX Release 6.0 (Platform Software Release C.60.00) (30216-90269)

156 Chapter 10
Technical Articles
IMAGE/SQL with TurboIMAGE/XL Enhancements
TurboIMAGE/XL Enhancements
The following are TurboIMAGE/XL enhancements, independent of SQL
access:
• Dynamic data set expansion for masters (MDX or DDXM)
• 80 GB data sets
• Performance Enhancement for databases with third-party indices
• DBSCHEMA and P type with odd sub-item length
• B-Tree indices
• Scalability for DBPUT, DBDELETE, and DBUPDATE (CIU on)
Dynamic Data Set Expansion for Masters
Dynamic data set expansion feature for non-jumbo (file size within 4
GB limit) detail data sets (DDX) was first released in MPE/iX 5.0. With
this release, this feature is available for non-jumbo master data sets
(MDX or DDXM) as well. The feature allows dynamic expansion of a
data set during DBPUT when the data set has approximated its current
capacity and DBPUT would fail unless the data set is expanded. As in
DDX, the capacity parameters which are maximum capacity, initial
capacity, and increment (optional), used for dynamic expansion, must
be set prior to the actual expansion. For new databases, these
parameters can be specified in the CAPACITY statement of the schema
definition to be processed by DBSCHEMA. For existing databases,
third-party tools which support MDX need to be employed.
The capacity parameters are:
• maximum capacity
is a required parameter and is a maximum number of entries the
data set can contain. It must be less than or equal to 2
31
−1
(2,147,483,647). The maximum capacity is adjusted by
TurboIMAGE/XL to represent a multiple of the blocking factor.
• initial capacity
is a required parameter and is the initial, primary, or hashing
capacity for the data set. It is the number of entries for which space
will be allocated and initialized when the data set is created. More
importantly, the initial capacity, and not the current capacity (initial
capacity with expansions included), will be used in the hashing
algorithm to calculate the primary address of the new entry being
added. If initial capacity is very low, there can be frequent
expansions which could result into both long synonym chains which
degrade the performance of some TurboIMAGE intrinsics and disk
fragmentation. Therefore, this number should be derived after
giving consideration to the expected volume of current data,