Plan file system support on Multiplatforms
Queue manager data is stored in the file system. A queue manager makes use of file system locking to prevent multiple instances of a multi-instance queue manager being active at the same time.
Shared file systems
Shared file systems enable multiple systems to access the same physical storage device concurrently. Corruption would occur if multiple systems accessed the same physical storage device directly without some means of enforcing locking and concurrency control. Operating systems provide local file systems with locking and concurrency control for local processes; network file systems provide locking and concurrency control for distributed systems.
Historically, networked file systems have not performed fast enough, or provided sufficient locking and concurrency control, to meet the requirements for logging messages. Today, networked file systems can provide good performance, and implementations of reliable network file system protocols such as RFC 3530, Network File System (NFS) version 4 protocol, meet the requirements for logging messages reliably.
Shared file systems and IBM MQ
Queue manager data for a multi-instance queue manager is stored in a shared network file system. On Microsoft UNIX, Linux, and Windows systems, the queue manager's data files and log files must be placed in shared network file system. On IBM i, journals are used instead of log files, and journals cannot be shared. Multi-instance queue managers on IBM i use journal replication, or switchable journals, to make journals available between different queue manager instances.
Prior to release v7.0.1, IBM MQ does not support queue manager data stored on networked storage accessed as a shared file system. If queue manager data is placed on shared networked storage, then we need to ensure the queue manager data is not accessed by another instance of the queue manager running at the same time.
From v7.0.1 onwards, IBM MQ uses locking to prevent multiple instances of the same multi-instance queue manager being active at the same time. The same locking also ensures that two separate queue managers cannot inadvertently use the same set of queue manager data files. Only one instance of a queue manager can have its lock at a time. Consequently, IBM MQ does support queue manager data stored on networked storage accessed as a shared file system.
Because not all the locking protocols of network file systems are robust, and because a file system might be configured for performance rather than data integrity, we must run the amqmfsck command to test whether a network file system will control access to queue manager data and logs correctly. This command applies only UNIX and IBM i systems. On Microsoft Windows, there is only one supported network file system and the amqmfsck command is not required.
- Requirements for shared file systems on Multiplatforms
Shared files systems must provide data write integrity, guaranteed exclusive access to files and release locks on failure to work reliably with IBM MQ.- Sharing IBM MQ files on Multiplatforms
Some IBM MQ files are accessed exclusively by an active queue manager, other files are shared.- Directory structure on UNIX and Linux systems
The IBM MQ directory structure on UNIX and Linux systems can be mapped to different file systems for easier management, better performance, and better reliability.- Directory structure on Windows systems
How to find queue manager configuration information and directories on Windows.- Directory structure on IBM i
A description of the IFS is given, and the IBM MQ IFS directory structure is described for server, client, and Java.Parent topic: Plan your storage and performance requirements on Multiplatforms
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