Isolation Levels for Secondary Data Replication Servers

If the UPDATABLE_SECONDARY configuration parameter is disabled (by being unset or by being set to zero), a secondary data replication server is read-only. In this case, only the Dirty Read or Read Uncommitted transaction isolation levels are available on High-Availability Data Replication (HDR) and Remote Standalone Secondary (RSS) servers.

If the UPDATABLE_SECONDARY parameter is enabled (by being set to a valid number of connections greater than zero), a secondary data replication server can support the Read Committed, Committed Read, or Committed Read Last Committed transaction isolation level, with or without the USELASTCOMMITTED session environment variable of the SET ENVIRONMENT statement. Only the DELETE, INSERT, UPDATE, and MERGE statements of SQL(and the dbexport utility, if the STOP_APPLY, USELASTCOMMITTED, and UPDATABLE_SECONDARY configuration parameters are set) can support write operations on an updatable secondary server.

Shared Disk Secondary (SDS) servers, however, can support the Read Committed, Committed Read, Committed Read Last Committed isolation levels, regardless of their UPDATABLE_SECONDARY setting. For more information about the UPDATABLE_SECONDARY configuration parameter, see the HCL OneDB™ Administrator's Reference.