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z/OS UNIX Temporary File System (TFS) Enhancements

By Lora Milczewski posted Wed March 25, 2020 12:09 PM



In z/OS V2R1 the Temporary File System (TFS) was enhanced to provide a warning for possible file system full situations, and allow for the TFS to be extended.

To assist with early warning of full TFS file systems, TFS provides a FSFULL parameter (-fsfull) to indicate a threshold and increments as to when a message (BPXTF009E, BPXTF010E, BPXTF011I) is issued concerning the percentage of used space. This will provide a similar capability as HFS and zFS with their FSFULL mount parameter. The valid range for both threshold and increment is 1-99.

TFS was enhanced to issue an eventual action message when it is 100% full regardless of the FSFULL setting. If FSFULL is not specified for a file system, FSFULL will be defaulted to a threshold of 99% with an increment of 5%, -FSFULL(99,5). This ensures FSFULL checking cannot be disabled.

The FSFULL threshold value is used to determine at what point a message is issued to indicate specific file system utilization. The increment is used to determine at what point a prior message is DOMed. If the file system continues to be utilized, another message is issued indicating the higher utilization. If the file system utilization decreases, another message is issued to indicate the lower utilization until the utilization goes below the threshold-increment percentage. These messages are eventual action messages. DOM of the message indicates the condition no longer exists. An additional hardcopy message will be issued when a file system is no longer at a threshold.

A modify command is provided to change the default FSFULL value (MODIFY tfs_proc_name,FSFULL(n,n)). This value will apply to subsequent TFS mounts that do not specify FSFULL. No modify command is available to alter the FSFULL setting for a file system that is already mounted.


In addition to the FSFULL parameter, to assist in avoiding possible application failures in situations where the file system becomes full, extension capabilities are provided. This capability allows a TFS to dynamically extend (BPXTF014I) a specified number of times both automatically (-ea) and manually (-em). A modify command is provided to change the default automatic and manual extend values (MODIFY tfs_proc_name, EA n and MODIFY tfs_proc_name,EM n). You can explicitly extend the TFS with a modify command (MODIFY tfs_proc_name,GROW) until the number of manual extends are exceeded (BPXTF015I). A maximum size and maximum number of extensions can be specified at mount time. The defaults for the automatic and manual settings are 0.


There is a query capability (MODIFY tfs_proc_name,Q) to display the number of extensions, limits, and default settings. 


The -fsfull, -ea, and -em parameters can be provided on the parmlib FILESYSTYPE TYPE(TFS) statement and the TFS type mount statement.


Note: Modify support is only available for a TFS that executes in a colony. PFSes do not have modify support in the kernel.


See the z/OS V2R1 z/OS UNIX manuals for details concerning the TFS enhancements.


See the entry with the following Blog entry for some experiences we had with these enhancements:

z/OS UNIX Temporary File System (TFS) Enhancements Experience