Altering/creating tables extended from CMDB is updating millions of rows for all records on all CMDB-extended tables. - Support and Troubleshooting

Altering/creating tables extended from CMDB is updating millions of rows for all records on all CMDB-extended tables. Description  Symptoms Altering/creating tables extended from CMDB is updating millions of rows for all records on all CMDB-extended tables.

Release Jakarta+

Cause The CMDB table uses an extension model called table-per-partition (TPP). TPP stores all extended tables on a flat set of database tables called partitions. Since all tables are stored as one single-flattened partition, changing one column on one extended table has to alter all rows at the database level. This process is performed via an "online alter". This allows the alter to take place on a temporary table to avoid locking the entire CMDB hierarchy during the process. Although the CMDB table is not entirely locked, this process is still very time consuming. Resolution This is expected platform behavior. Although this is allowed, it is important to understand the extension models used by ServiceNow before performing database schema changes. Additional Information Documentation topic: Table flattening