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DB2 Manager User Guide 47
StorageTek Proprietary
The following control region components are illustrated in Figure 4:
• Control processor. This component is responsible for initiation and
termination of the control region, and for processing operator
requests.
• Writer tasks. There will be one or more writer tasks – the number of
writer tasks is controlled via the MAXTWTR initialization parameter.
A single writer task will be used exclusively for storage of migrated
rows in an Archive Manager database, during execution of the DB2
Manager table migration utility. The existence of multiple writer
tasks will enable multiple row migration jobstreams to be executed
concurrently on different Archive Manager databases.
• Tape reader tasks. There will be one or more tape reader tasks – the
number of these tasks is controlled by the MAXTRDR initialization
parameter. A tape reader task will be invoked by the DB2 Manager
SQL intercept processor during object retrieval, update and deletion
processing, when a migrated row is to be retrieved from a tape-
resident Archive Manager object. Each reader task will be able to
process a single tape volume at any one time. The number of tape
reader tasks controls the number of tape volumes which may be
processed concurrently for this type of processing.
• Disk reader tasks. There will be one or more disk reader tasks – the
number of these tasks is controlled by the MAXDRDR initialization
parameter. A disk reader task will be invoked by the DB2 Manager
SQL intercept during object retrieval, update and deletion processing,
when a migrated row is to be retrieved from a disk-resident Archive
Manager object. The number of disk reader tasks controls the
number of disk retrieval requests which may be processed
concurrently.
• Scheduler tasks. There will be one or more scheduler tasks – the
number of these tasks is controlled by the MAXSCHED initialization
parameter. A scheduler task is responsible for validating requests
received from the DB2 Manager SQL intercept processor, and
assigning the request to an appropriate reader or writer task.
Increasing the number of scheduler tasks will reduce the length of
time a request waits for validation and assignment processing, but will
increase the processing overhead associated with the control region.
• Housekeeping task. A single housekeeping task will be initiated
during control region initialization processing. It is responsible for
monitoring outstanding requests, and terminating stalled requests.