The Unique Numbers page allows the system administrator to modify the last sequence number used for a sequence as well as set the block size of unique numbers that should be loaded in the application server.
The Sequence Name specifies the name of the sequence and uniquely identifies the sequence. The reserved Sequence Name of ALL is the default sequence and it is used if any application request for a unique number is made without specifying the Sequence Name.
Sequence Last ID specifies the last assigned unique number for this particular sequence.
Sequence Block Count specifies the set of numbers that should be assigned to the application server on each unique number request to the database. A database request for the next unique number block is only made after all of the unique numbers have been exhausted on the application server.
Unique numbers used in the system are generated based on entries maintained in the unique numbers table. Take care whenever you update the Sequence Last ID to ensure that duplicate unique numbers are not generated by the system. The Sequence Block Count for any unique number sequence should be set after consideration of the transaction behavior in any installation. The Sequence Block Count indicates the range of unique numbers each logical application server keeps in memory before requiring a database call to the TABLE_NM to get a new range. Thus, if the range is set too high and the application server is shut down for any reason, the unused range of numbers kept in memory can no longer be used. For example, if a value of 1000 was used and three logical application servers requested a unique number range and then were immediately shut down, you could waste a range of 3000 unique number values. Thus, you must consider how quickly unique numbers may be wasted, in addition to considering the performance gains achieved by setting a high value for Sequence Block Count.