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Converting DB2 to Systems Managed Storage 77
8.4 Positioning for Implementation
For the DBA, there are a number of items to be considered as prerequisites for
the process.
8.4.1 Prerequisite Planning
Categorize each data type into separate groups
The usage characteristics and service requirements will have to be considered
for each data type, and will include:
• Response time performance
• Accessibility and availability operations
• Initial sizing of data sets and future growth
• Difference between production and user/testing data sets
DB2 STOGROUPs Mapping to SMS Storage Groups
To ensure consistency, it is recommended that DB2 STOGROUPs are converted
to equivalent SMS Storage Groups.
Identify DB2 Data Sets Eligible for HSM Management
Decide for which groups of DB2 data DFSMShsm should have the authority to
migrate or backup. For example, production databases, Active logs, System
libraries, and BSDS are candidates for NO MIGRATION due to their critical
status.
Set DSNZPARM to have DFSMShsm automatically recall DB2 data sets during
DB2 access. Set RECALL to Y. Set RECALLD, the maximum wait for DFSMShsm
to complete recreation of data sets on the primary disk, based on testing with
typical end user databases.
Use of Guaranteed Space
As part of the initial phase,the GUARANTEED SPACE option can be used to
position data, particularly production tablespaces, and active logs. Once satisfied
with the allocation of the data sets, it is recommended that this option be
removed, so future allocations can be under the sole control of SMS.
Guaranteed space is recommended for use only during the migration period (from
DB2 managed to SMS managed) which should be kept short to prevent failures
on initial allocation and data set extension. Unlike non-SMS, SMS does not retry
allocation on another volume if the requested space cannot be satisfied on the
specified candidate volume.
Guaranteed space is not useful unless the space requirements are relatively
small and static.
Ensure That All Data Sets Are Cataloged
SMS requires that all data sets are cataloged in ICF catalogs, enabling the use of
standard catalog search routines (VSAM and CVOL catalogs are no longer
supported after 1999). For further information see, DFSMS/MVS Managing
Catalogs, SC26-4914.