The table below shows the operation modes of the rebalancing utility.
Table 10-1 Operation modes of the rebalancing utility
Operation mode | Description |
---|---|
Shared mode | Accesses to the table are permitted during execution of pdrbal. Use this mode for a system that cannot stop online applications due to 24-hour operation. |
Exclusive mode | Accesses to the table are not permitted during execution of pdrbal. Use this mode for a system that can deny access to the table and execute batch processing at night. |
In the shared mode, a table being rebalanced is accessible. To execute the utility in the shared mode, specify share in the -k option.
The shared mode requires acquisition of log information as well as repeated allocation and release of the resources that are required by concurrently executing SQL. Therefore, the time required for a rebalance operation in the shared mode is longer than in the exclusive mode.
The time required for the rebalancing operation might also be longer when compressed tables are rebalanced in the shared mode than when there are no compressed columns. This is because the utility expands and compresses the data in the compressed columns when it moves the data. In this case, the KFPL33509-W message is issued, but the rebalancing operation continues. If you want to reduce the execution time, use the pdcancel command to cancel the rebalancing operation in the shared mode, and then re-execute the operation in the exclusive mode.
Figure 10-3 Example of rebalancing utility execution in shared mode
In the exclusive mode, no access is allowed to a table being processed by the rebalancing utility. To execute the rebalancing utility in the exclusive mode, specify exclusive in the -k option.
In the exclusive mode, acquisition of log information is optional. The required resources are allocated and released only once, and batch index creation is permitted; therefore, the time required for the rebalancing operation is less than in the shared mode.
Figure 10-4 Example of rebalancing utility execution in exclusive mode