Specify data guarantee level 0 to allow other users to view data being updated without waiting for update completion. This guarantee level can improve the concurrent execution capability more than the other guarantee levels. However, if the same rows are searched twice in the same transaction, the first and second search results may not be the same.

Figure 4-49 shows the data guarantee range of data guarantee level 0.

Figure 4-49 Data guarantee range of data guarantee level 0

Specify data guarantee level 1 to prevent other users from updating data that has been searched once until the search processing is completed (until HiRDB finishes viewing the pages or rows). This guarantee level therefore improves the concurrent execution capability. However, if the same rows are searched twice in the same transaction, the first and second search results may not be the same.

Figure 4-50 shows the data guarantee range of data guarantee level 1.

Figure 4-50 Data guarantee range of data guarantee level 1

Specify data guarantee level 2 to prevent other users from updating data that has been searched once until the transaction ends. Data that has been searched is therefore guaranteed until the end of the transaction. However, data that has not been searched is not guaranteed. If the same rows are searched twice in the same transaction, the first and second transaction results may not be the same if there are added rows.

Figure 4-51 shows the data guarantee range of data guarantee level 2.

Figure 4-51 Data guarantee range of data guarantee level 2

1. If data guarantee level 0 is specified for a cursor declaration that accompanies an update, the specification is ignored, and level 1 is assumed.
2. If data guarantee level 0 or 1 is specified for a holdable cursor, the specification is ignored, and level 2 is assumed.