CREATE TABLE "DBA".IQ_MPX_STATUS ( server_name varchar(30) NOT NULL, oldest_version unsigned bigint NOT NULL, current_version varchar(10) NOT NULL, catalog_version unsigned bigint NOT NULL, )
This table contains dynamic information to support management of old table versions in a multiplex environment. The information in this table changes as transactions begin or commit on servers of the multiplex.
Each server updates its own row in the table automatically on transaction-commit and begin-transaction. SQL Remote propagates changes between the multiplex servers. UPDATE permission is not granted to PUBLIC.
server_name The server name of this server.
oldest_version The version number of the oldest active transaction on this server.
current_version The current transaction number on this server.
catalog_version Each time the write server modifies the table schema, the catalog_version advances to the current_version. Each time you synchronize query servers, the catalog_version at a query server advances to the write server’s version, but remains static until the next synchronization.
By examining the catalog_version column, you can see easily whether query servers are synchronized.
For example, SQL statements such as CREATE, DROP, and ALTER, which modify tables in the IQ Store, increment catalog_version. Once IQ Store tables are modified, query servers cannot see versions of objects subsequently committed in the IQ Store. Query servers must be synchronized to see versions of objects in the IQ Store committed after the statement modified the IQ Store table schema.
