In-memory row-level versioning (RLV) is supported in multiplex from IQ 16.0 SP08.
The RLV store, resides on the coordinator, making it the RLV writer. All other nodes in the multiplex are RLV readers. On the RLV writer, you can execute DDL, DML and query data.
On RLV readers, data in RLV-enabled tables is available to queries, but modification of data and schema is not allowed.
For queries involving RLV-enabled tables executing on RLV readers:
The RLV reader makes an ODBC connection to the RLV writer.
Only the part of the query referencing RLV-enabled tables is forwarded to and executed on the RLV writer.
Results are then sent back to the RLV reader.
All non-RLV-enabled table portions of the query execute on the RLV reader.
Configure RLV Memory
RLV memory is configured in addition to existing IQ cache memory. The host machine must have enough memory for both the RLV memory and the IQ main buffer cache, which are independent memory pools.
The maximum size of the RLV store, for all tables, is specified with a server option, which can be set with:
The server startup switch -iqrlvmem specifying the
The sa_server_option system procedure specifying the rlv_memory_mb,
A size of 2 GB or greater is recommended. If the server switch is not specified, the value defaults to 2 GB.
When defined using either method, if the value exceeds 2/3rds of the system virtual memory limit, the server generates an error.