For z/OS Release 2, UNIX System Services offers improved application flexibility, new tools for managing e-business, and greater ease of use. Highlights include:
Enhanced ASCII functionality makes it easier to port internationalized applications developed on (or for) ASCII platforms to z/OS platforms, by providing conversion from ASCII to EBCDIC and from EBCDIC to ASCII.
Enhanced ASCII introduces:
- A file tagging mechanism, which allows programmers to tag files with a file attribute that describes the contents of the file. The file tag contains a Coded Character Set Identifier (CCSID) that identifies the character set of the text data within the file, and indicates whether the file is eligible for automatic conversion.
- Support for automatic data conversion between character sets when the CCSIDs of a program and a file it is reading or writing to are different.
Enhanced ASCII support applies only to z/OS UNIX files; it does not apply to MVS files, even if they can be accessed by z/OS UNIX. For more information about the limitations of Enhanced ASCII, see z/OS C/C++ Programming Guide.
Specific changes in support of Enhanced ASCII include:
- A new statement in the BPXPRMxx parmlib member, AUTOCVT(ON|OFF), globally enables and disables the automatic text conversion of I/O data between code sets. AUTOCVT can be turned on or off with the SETOMVS and SET OMVS operator commands. Automatic conversion can also be overridden by individual programs at a thread level using flags in the thread control block.
- The MOUNT statement in BPXPRMxx has a new keyword, TAG, which specifies whether files should be converted during reading and writing.
- The TSO/E MOUNT command has a new operand, TAG(NOTEXT|TEXT,ccsid) to support file tagging.
- Shell commands are added or changed to support file tagging and automatic file conversion:
- A new shell command, chtag, assigns, changes, and removes the file tag on existing files.
- The new -T option on the cksum shell command enables the automatic conversion of tagged files.
- The new -B option on the cmp shell command disables the automatic conversion of tagged files.
- The new tag option on the automount command specifies whether file tags for untagged files in the mounted file systems are to be implicitly set.
- New options on the cp, df, file, find, head, icnov, localedef, ls, mount, mv, od, pack, pax, strings, tail, tcsh, and test shell commands support file tagging and/or automatic file conversion.
- Two new environment variables are added to support file tagging and automatic file conversion. BPXK_AUTOCVT enables the conversion of data between EBCDIC and ASCII code sets, and _BPXK_CCSIDS identifies an EBCDIC or ASCII pair of corresponding CCSIDs. (Only one pair is supported with this release: EBCDIC 1047 and ISO-8859-1.)
- New shell variables (_TAG_REDIR_IN, _TAG_REDIR_OUT, and _TAG_REDIR_ERROR) control the conversion of untagged files. (See the descriptions of the sh and tcsh commands in z/OS UNIX System Services Command Reference.)
- The BPX1FCT callable service controls the automatic conversion of file data with two new arguments. F_SETTAG sets the file tag, and F_CONTROL_CVT controls automatic file conversion.
- HFS control
The new FACILITY class profile BPX.DAEMON.HFSCTL enforces program control for HFS programs only. When users are given permission to this profile, z/OS UNIX bypasses program control rules for programs loaded from MVS libraries, but enforces the rules for HFS programs.
- Soft shutdown for mounted file systems
This enhancement allows files systems to be unmounted without the loss of data. A new keyword on the MODIFY operator command, SHUTDOWN=FILESYS, specifies that all active file systems on this system are to be unmounted and the data synched to disk. In a sysplex environment, AUTOMOVE(YES) file systems that are owned by this system are moved to another system.
- A new file system, zFS, which can be used in addition to HFS
zServer File System (zFS) is a new file system for z/OS UNIX System Services that can improve performance for many applications, especially those that access very large sequential files. For more information about zFS, see Distributed File Service zFS Administration.
- Support for the TCP/IP Services resolver enhancement
The TCP/IP Services resolver enhancement provides common functionality across native MVS and z/OS UNIX environments. The key functions for the various z/OS resolver libraries, which are used by TCP/IP Services applications for name-to-address or address-to-name resolution, are consolidated into a new, single resolver component.
- A new BPXPRMxx statement, RESOLVER_PROC, specifies the name of a cataloged procedure in SYS1.PROCLIB that will be used to start the resolver address space during z/OS UNIX initialization.
- DISPLAY OMVS,O displays the RESOLVER_PROC specification.
- Two new callable services, gethostbyname(BPX1GHN) and gethostbyaddr (BPX1GHA), provide access to the system resolver functions.
- Enhancement to uname utility for OS/390 to z/OS compatibility
The uname utility has a new option that allows for continued support of the name OS/390 within the uname() field.