Understanding namespace validation and correction
zFS provides namespace validation and correction in a shared file system environment. First, it is important to understand the concept of a namespace. zFS communicates between sysplex members using XCF protocols. The zFS XCF protocol exchanges information among members about zFS ownership and other attributes of zFS mounted file systems. This information, which is kept in the memory of each zFS member, is called the zFS namespace. If zFS members do not agree on the zFS owner of each file system, there might be problems that require a zFS restart or an IPL to recover.
- When an administration command experiences an XCF message timeout
- Automatically at zFS initialization
- Automatically when zFS detects a problem that might be because of a namespace inconsistency
- Explicitly using the MODIFY ZFS,NSVALIDATE operator command.
- Updating the inconsistent information
- Automatically remounting a file system
- Internally restarting zFS on one or more members.
Each zFS only keeps track of file systems that are locally mounted. z/OS® UNIX locally mounts file systems on systems where the mount was issued (or directed to through the SYSNAME parameter), and for sysplex-aware file systems, on other systems. z/OS UNIX keeps mount information that is hardened in the couple data set. In addition, zFS keeps track of zFS ownership by using cross system ENQ. The zFS owner of an aggregate always has an exclusive ENQ with a qname of SYSZIOEZ and an rname of IOEZLT.aggregatename. In this way, zFS hardens zFS ownership information in an independent repository. When an inconsistency is detected in the zFS namespace information between zFS members, this hardened information can be queried to determine how to automatically correct the inconsistency.