Siebel Anywhere Administration Guide > Supplementary Information for Specific Upgrade Types > Performing Database Schema Updates >

About What Happens During a Database Schema Upgrade

This section provides background information about what happens during a database schema upgrade.

During database schema upgrades, new and changed objects are identified by comparing the current physical schema with the new virtual schema. Based on this comparison, Upgrade Wizard adds new objects and alters existing objects by using the following:

  • To create the new objects: create table, create index, and so on.
  • To alter the existing objects: alter table, alter index, and so on.

CAUTION:  Downsizing existing columns is not recommended. Do not drop columns or tables. These operations can cause transactions that were created before the schema change to be rejected, because data that was included in the earlier transactions may not fit into the new database schema.

Normally, the database does not allow downsizing a column that already contains data that could not fit into a new smaller column. If you downsize a column, the column representation in the repository would be different from the physical schema. Under these conditions, Siebel Remote would fail, among other possible errors.

For example, after downsizing existing columns, one of the columns in the new database is shorter (it is created from the representation in the repository). Then, a local database is reextracted (this includes a new schema). After the Remote user synchronizes, initialization occurs. Upgrade Wizard first applies the new local database (including a new schema) to a Remote user's machine. Next, Upgrade Wizard applies any server transactions downloaded during synchronization. If these transactions were generated before the schema changed, Upgrade Wizard tries to insert data that does not fit into the new column, causing the transaction to be rejected. Furthermore, if this occurs on a regional node, the error may cause an outage.

Siebel Anywhere Administration Guide