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Native Mode Message File Enhancements by Joe-Sue Wang Commercial Systems Divison Native Mode Implementation Message files are used as a way of communicating between processes using the MPE/iX file system. Beginning with MPE/iX Release 5.0, message files are supported in native mode. There is no change in the internal structure of a message file, and all the current functionalities and intrinsic interfaces also remain unchanged. The native mode message file implementation is transparent to you, the end-user. Current functionalities provided by message files are fully described in the the Interprocess Communication Programmer's Guide (32650-60011). This article describes the enhancements added with the native mode message file implementation. Increased Number of Concurrent Writers A writer is identified when a process opens a message file with write access. Concurrent writers are writers accessing a message file at the same time. When message files were supported in compatibility mode (CM), a maximum of 384 writers could write to the same message file simultaneously. This limitation resulted from the size of a CM table used by message files. The maximum number of concurrent writers has been significantly increased in MPE/iX Release 5.0. Since it is a native mode implementation, there is no longer any size restriction in the new tables. Similar to the compatibility mode implementation, a unique 16 bit writer ID number is written as part of the data to a message file for each FWRITE intrinsic call; therefore, the limiting factor for the maximum writers comes from this 16 bit writer ID. The maximum number of concurrent writers is now 32,768. Increased I/O Performance In general, both compatibility mode and native mode applications benefit from the performance of native mode message files. In our test environment, the I/O performance of compatibility mode applications using message files was up to two times higher. Native mode applications showed even better results in message throughput. However, since performance improvement is dependent on how message files are used by the application, performance may vary. Beginning with this MPE/iX release, native mode applications using message files should signigicantly outperform the same applications running in compatibility mode. Increased File Size With the native mode implementation, message files are native mode files; therefore, their file size can be increased up to 4 gigabytes. FFILEINFO Change A new item number, 93, has been added to FFILEINFO. It returns the software interrupt PLABEL in a 32 bit long value. The new item number should be used for applications that arm the software interrupt in native mode. The existing item number 49 in FFILEINFO is still available and returns a 16 bit compatibility mode PLABEL. Applications that arm the software interrupt in compatibility mode should continue to use item number 49.