IRIX Base Documentation 2002 November

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INTRO_FFIO(3F) Last changed: 3-1-99 NNAAMMEE IINNTTRROO__FFFFIIOO - Describes performance options available with the FFIO layers IIMMPPLLEEMMEENNTTAATTIIOONN See individual man pages for implementation details. DDEESSCCRRIIPPTTIIOONN The Flexible File I/O (FFIO) system lets the user specify a comma- separated list of layers through which I/O data is to be passed. This is done by providing a value for the _s_p_e_c argument to the --FF option on the aassssiiggnn(1) command. This specifies a _c_l_a_s_s of processing to be done on the data. The following C routines are used with FFIO: * ffffffccnnttll(3C): performs functions on files opened using FFIO * fffflliissttiioo(3C): initiates a list of I/O requests using FFIO * ffffiioolloocckk(3C): locks and unlocks function calls * ffffooppeenn(3C): opens or closes a file using FFIO * ffffppooss(3C): positions files opened using FFIO * ffffrreeaadd(3C): reads from a file using FFIO * ffffrreeaaddaa(3C): provides asynchronous read using FFIO * ffffsseeeekk(3C): repositions a FFIO file * ffffwwrriitteeaa(3C): provides asynchronous write using FFIO * ffffsseettsspp(3C): initiates EOV processing for files opened using FFIO * ffffwwrriittee(3C): writes to a file using FFIO FFFFIIOO oonn IIRRIIXX ssyysstteemmss The default layer for direct access on IRIX systems is the ccaacchhee layer and it does not have the coherency to handle multiple processes doing I/O to the same file. The user must assign the direct access file to either the ssyysstteemm or gglloobbaall layer for programs to work as expected with more than one process. On IRIX systems, the FFIO library calls aaiioo__ssggii__iinniitt the first time it issues an asynchronous I/O call. It passes the following parameters to aaiioo__ssggii__iinniitt: aio_numusers=MAX(64,sysconf(_SC_NPROC_CONF)) aio_threads=5 aio_locks=3 If a program is using multiple threads and asychronous I/O, it is important that the value of aaiioo__nnuummuusseerrss be at least as large as the number of sprocs and pthreads that the application contains. For more information, see the aaiioo__ssggii__iinniitt man page on IRIX systems. Users can change these values by setting the following environment variables to the desired value: * change FFFF__IIOO__AAIIOO__TTHHRREEAADDSS to modify aaiioo__tthhrreeaaddss * change FFFF__IIOO__AAIIOO__LLOOCCKKSS to modify aaiioo__lloocckkss * change FFFF__IIOO__AAIIOO__NNUUMMUUSSEERRSS to modify aaiioo__nnuummuusseerrss The following example causes aaiioo__tthhrreeaaddss to be set to 8 when the FFIO routines call aaiioo__ssggii__iinniitt: setenv FF_IO_AIO_THREADS 8 Users can also supersede the FFIO library's call to aaiioo__ssggii__iinniitt by calling it themselves, before the first I/O statement in their program. The following layers can issue asynchronous I/O calls on IRIX systems: * ccooss: see the later description on this man page for a description of how the ccooss layer uses asynchronous I/O. * ccaacchheeaa and bbuuffaa: users should assume that these layers may issue asynchronous I/O calls. * ssyysstteemm or ssyyssccaallll: these layers may issue asynchronous I/O calls if called from a BBUUFFFFEERR IINN or BBUUFFFFEERR OOUUTT statement, or from the ccooss or ccaacchheeaa layer. The ssyysstteemm and ssyyssccaallll layer may also issue asynchronous I/O calls if called via ffffrreeaaddaa(3C), ffffwwrriitteeaa(3C), or fffflliissttiioo(3C) (all deferred on IRIX systems). SSppeecciiffyyiinngg FFFFIIOO LLaayyeerrss The _s_p_e_c argument of the --FF option of the aassssiiggnn(1) command comprises a list of layers or filters that are used to manipulate the data file as it is being read or written. The available layers include performance options (such as memory-resident and SDS-resident files) and the capability to read and write files in a variety of different vendors' blocking formats. Each layer _s_p_e_c is of the general form: _c_l_a_s_s[._t_y_p_e[._s_u_b_t_y_p_e]][:_n_u_m_1]:[_n_u_m_2]:[_n_u_m_3]] Many of the layers also allow you to specify the numeric parameters with a keyword. On UNICOS and UNICOS/mk systems, this requires that your application be linked with Cray Research's CrayLibs 3.0 or later releases. The format for these specifications is given in the description of each layer where the specification is available. Selected layers are available on IRIX systems. The available platforms are detailed in each layer's description. For more information about FFIO, see the _A_p_p_l_i_c_a_t_i_o_n _P_r_o_g_r_a_m_m_e_r'_s _I/_O _G_u_i_d_e. The _s_p_e_c argument can have the following values: CCllaassss EExxppllaannaattiioonn bbllaannkkxx or bbllxx Blank compression filter. This layer is used as a filter to compress or decompress blanks in character data. Not available on IRIX systems. _t_y_p_e can be one of the following: ccooss COS-style blank compression (bbllxxcchhrr=27 or Ox10) ccttssss CTSS-style blank compression (bbllxxcchhrr=48 or 0x30) cc220055 CYBER 205-style blank compression (bbllxxcchhrr=48 or 0x30) _n_u_m_1 is the decimal value of the ASCII character used as the escape code to control the blank compression (usually EESSCC or 27). _n_u_m_2 is the decimal value of the ASCII character that is the object of the compression (usually BBLLAANNKK or 32). You can specify the numeric parameters with this alternate keyword syntax: bbllxx[[.._t_y_p_e]][[..bbllxxcchhrr==_n_u_m_1]][[..bbllnnkk==_n_u_m_2]] bbllaannkkxx[[.._t_y_p_e]][[..bbllxxcchhrr==_n_u_m_1]][[..bbllnnkk==_n_u_m_2]] bbmmxx Tape I/O. Each logical record requested is a physical tape block. Deferred implementation on IRIX systems. The _n_u_m_1 field represents the size of each buffer, in 4096-byte blocks. The _n_u_m_2 field represents the number of buffers. On UNICOS systems, files on ER90 volumes that have been mounted in blocked mode may use this layer (see the _T_a_p_e _S_u_b_s_y_s_t_e_m _U_s_e_r'_s _G_u_i_d_e, for information about restrictions on record sizes when using ER90 block mode). You can specify the numeric parameters with this alternate keyword syntax: bbmmxx[[..bbuuffssiizzee==_n_u_m_1]][[..nnuumm__bbuuffffeerrss==_n_u_m_2]] bbuuffaa Asynchronous buffering layer. Available on IRIX systems. The bbuuffaa layer provides asynchronous buffering. It allows efficient sequential-access I/O. The _n_u_m_1 field represents the size in 4096-byte blocks of each buffer. The maximum value for _n_u_m_1 on IRIX systems is 32,767. The maximum allowed value on UNICOS and UNICOS/mk systems is 1,073,741,823 (you may not be able to use a value of this size because that amount of memory may not be available). The _n_u_m_2 field selects the number of buffers to be used. You can specify the numeric parameters with this alternate keyword syntax: bbuuffaa[[..bbuuffssiizzee==_n_u_m_1]][[..nnuumm__bbuuffffeerrss==_n_u_m_2]] cc220055 CDC CYBER 205/ETA records. Not available on IRIX systems. The CYBER 205-type W record can be selected by specifying cc220055..ww. The _n_u_m_1 field is not permitted. The _n_u_m_2 field represents the size of the working buffer, in bytes, used in record blocking. If any logical records written exceed this size, a major performance penalty can result. The _t_y_p_e field should be specified as ww. The best performance is currently obtained when _n_u_m_2 is greater than the largest record to be processed plus 16 bytes. You can specify the numeric parameters with this alternate keyword syntax: cc220055[[..ww]][[..bbuuffssiizzee==_n_u_m_2]] ccaacchhee Cached file. The ccaacchhee layer allows efficient random-access I/O, even when file access is clustered in several regions of a file. Available on IRIX systems. During reads and writes to the layer, cache buffers frequently must be preempted. The buffer chosen for preemption is always the least recently accessed buffer at the time of preemption. The options available are ..mmeemm, which specifies that buffers reside in memory or ..ssddss, which specifies that buffers reside in the SDS. (..ssddss is not supported on CRAY T3E systems or IRIX systems). Memory-resident buffers are the default. The numeric fields are as follows: * _n_u_m_1 is the size in 4096-byte blocks of each cache page. The maximum value for _n_u_m_1 on IRIX systems is 32,767. The maximum allowed value on UNICOS and UNICOS/mk systems is 1,073,741,823 (you may not be able to use a value of this size because that amount of memory may not be available). * _n_u_m_2 selects the number of cache pages to be used. * _n_u_m_3 is the size in 4096-byte blocks at which the ccaacchhee layer attempts to bypass ccaacchhee layer buffering. If a user's I/O request is larger than _n_u_m_3, the request might not be copied to a cache page. The default on IRIX systems is _n_u_m_3=_n_u_m_1. The default on UNICOS and UNICOS/mk systems is _n_u_m_3=_n_u_m_1*_n_u_m_2. You can specify the numeric parameters with this alternate keyword syntax: ccaacchhee[[.._t_y_p_e]][[..ppaaggee__ssiizzee==_n_u_m_1]][[..nnuumm__ppaaggeess==_n_u_m_2]] [[..bbyyppaassss__ssiizzee==_n_u_m_3]] ccaacchheeaa Asynchronously cached file. Available on IRIX systems. This type of processing usually performs well whenever the ccaacchhee layer might be used. In addition, any sequential forward and sequential backward access through the file is detected. When sequential access patterns are detected while reading, asynchronous read-ahead is performed provided that the numbers of pages to read ahead has been specified. When writing, selective asynchronous write-behind is performed. The values for _t_y_p_e are ..mmeemm, which specifies that buffers reside in memory, or ..ssddss, which specifies that buffers reside in the SDS (..ssddss is not supported on CRAY T3E systems or on IRIX systems). Memory-resident buffers are the default. The numeric fields are as follows: * _n_u_m_1 is the size in 4096-byte blocks of each cache page. The maximum value for _n_u_m_1 on IRIX systems is 32,767. The maximum allowed value on UNICOS and UNICOS/mk systems is 1,073,741,823 (you may not be able to use a value of this size because that amount of memory may not be available). * _n_u_m_2 selects the number of cache pages to be used. * _n_u_m_3 selects the number of pages to read ahead asynchronously. The default is 0. * _n_u_m_4 selects a shared cache number in the range of 1 to 15. If _n_u_m_4 is 0, a private cache is indicated. You can specify the numeric parameters with this alternate keyword syntax: ccaacchheeaa[[.._t_y_p_e]][[..ppaaggee__ssiizzee==_n_u_m_1]][[..nnuumm__ppaaggeess==_n_u_m_2]] [[..mmaaxx__lleeaadd==_n_u_m_3]][[..sshhaarreedd__ccaacchhee==_n_u_m_4]] On IRIX systems, stacked shared ccaacchheeaa layers are not supported. On UNICOS and UNICOS/mk systems, stacked shared ccaacchheeaa layers are supported, but in multitasked programs, different files must not mix the order of the shared caches. Examples: The following specifications ccaannnnoott both be used by a multitasked program: * aassssiiggnn --FF ccaacchheeaa::::::::11,,ccaacchheeaa::::::::22 uu::11 * aassssiiggnn --FF ccaacchheeaa::::::::22,,ccaacchheeaa::::::::11 uu::22 The following specifications ccaann both be used by a multitasked program on a UNICOS system: * aassssiiggnn --FF ccaacchheeaa::::::::11,,ccaacchheeaa::::::::22 uu::11 * aassssiiggnn --FF ccaacchheeaa::::::::11,,ccaacchheeaa::::::::22 uu::22 ccddcc CDC 60-bit format _t_y_p_e. Not available on IRIX systems. No numeric fields are accepted. The supported values for _t_y_p_e are as follows: _t_y_p_e FFoorrmmaatt iiww I-type blocks, W-type records ccww C-type blocks, W-type records ccss C-type blocks, S-type records cczz C-type blocks, Z-type records The _s_u_b_t_y_p_e field accepts one of the following values that indicate the presence of block trailers and other low-level characteristics: _s_u_b_t_y_p_e VVaalluuee ddiisskk Disk type structure, for use with station transfers of CYBER datasets ii NOS internal tape format ssii System internal or SCOPE internal tape format ccooss or bblloocckkeedd COS blocking. Available on IRIX systems. If specified, _t_y_p_e must be one of the following: _t_y_p_e AAccttiioonn ssyynncc Uses a single buffer in the blocking and deblocking process. I/O is done strictly synchronously. aassyynncc Divides the buffer into two parts and uses asynchronous I/O to transfer the blocked data between the buffer(s) and the logical device. When reading, asynchronous read-ahead is performed, and when writing, asynchronous write-behind is performed. To effectively use aassyynncc, the buffer size should be at least twice the record length. aauuttoo Default (if _t_y_p_e is not specified). Chooses either synchronous or asynchronous behavior depending on the buffer size. If the buffer size is less than 64 blocks, synchronous behavior is selected. If it is greater than or equal to 64 blocks, asynchronous behavior is selected. For _n_u_m_1, enter the desired buffer size in 4096-byte blocks (for example, --FF ccooss::4422 requests COS blocking and a 42-block buffer). The _n_u_m_1 value also determines the record size for underlying layers which perform record blocking. The underlying record size is _n_u_m_1 blocks if in synchronous mode and _n_u_m_1/2 or _n_u_m_1/2+1 blocks if in asynchronous mode. For an underlying tape layer, the record size is the tape block size. MIPSpro 7.3/PE 3.3 release: If not specified, the default buffer size is the larger of the following: the large I/O size (UNICOS and UNICOS/mk systems only), the preferred I/O block size (see the ssttaatt(2) man page), or 48 blocks. Furthermore, if _t_y_p_e is aauuttoo (the default), then the default buffer size is doubled if asynchronous mode is used (the ccooss layer automatically switches to asynchronous mode). You can specify the numeric parameters with this alternate keyword syntax: ccooss[[.._t_y_p_e]][[..bbuuffssiizzee==_n_u_m_1]] eerr9900 ER90 I/O. Not available on IRIX systems or on CRAY T3E systems. Each I/O operation results in a corresponding system call. Adjacent records are not delimited from one another. No subfields are accepted. The byte-stream mode of the device must be used. See ttppmmnntt(1). eevveenntt I/O layer monitoring. Available on IRIX systems. The eevveenntt layer monitors I/O occurring between two layers on a per-file basis. This layer generates statistics in an ASCII log file; users can specify what type of report is generated. The eevveenntt layer is enabled by default. Users do not have to relink their programs to study I/O performance. To generate information, rerun the program with the eevveenntt layer specified on the aassssiiggnn command. Statistics are reported to ssttddeerrrr by default. The FFFF__IIOO__LLOOGGFFIILLEE environment variable can be used to name a file to which statistics are written by the eevveenntt layer. The default action is to overwrite the existing file. To append information to an existing file, specify a plus sign (++) before the file name. The eevveenntt layer reports counts for rreeaadd, rreeaadd, wwrriittee, and wwrriitteeaa. These counts represent the number of calls made to to an FFIO layer entry point. In some cases, the ssyysstteemm layer may actually use a different I/O system call, or multiple system calls. For example, the rreeaaddaa system call does not exist on IRIX systems, and the ssyysstteemm layer rreeaaddaa entry point will use aaiioo__rreeaadd(()). On IRIX systems, the report that is generated may include mention of the "lock" layer, even though the lock layer may not have been specified by the user. On CRAY T3E systems, if more than one process is using the eevveenntt layer, and you set the FFFF__IIOO__LLOOGGFFIILLEE environment variable, you must use the plus sign (++) before the file name to prevent _p_r_o_c_e_s_s _a from overwriting the information written by _p_r_o_c_e_s_s _b. Using the plus sign also means that the information will be appended to an existing file. On CRAY T3E systems you can also use the FFFF__IIOO__LLOOGGFFIILLEEPPEE environment variable to name a file to which statistics are written. The file name will be _x._n, where _x is the name specified by the environment variable and _n is the number of the PE which wrote the file. The default action is to overwrite the existing file. To append information to the existing file, specify a plus sign (++) before the file name. Enter one of the following for _t_y_p_e: vvaalluuee IInnffoorrmmaattiioonn rreeppoorrtteedd nnoossttaatt No statistical information is reported. ssuummmmaarryy Information on event types that occur at least once are reported. bbrriieeff A one-line summary for layer activities is reported. ff7777 FORTRAN 77/UNIX Fortran record blocking. This is the common blocking format used by most FORTRAN 77 compilers on UNIX systems. Available on IRIX systems. Enter one of the following for _t_y_p_e: _t_y_p_e FFoorrmmaatt nnoonnvvaaxx Default. Control words in a format common to machines such as the MC68000. vvaaxx VAX format (byte-swapped) control words. Not available on IRIX systems. The specification of vvaaxx or nnoonnvvaaxx is not relevant to data conversion. For _n_u_m_1, enter the maximum record size in bytes. For _n_u_m_2, enter the working buffer size, in bytes. You can specify the numeric parameters with this alternate keyword syntax: ff7777[[.._t_y_p_e]][[..rreeccssiizzee==_n_u_m_1]][[..bbuuffssiizzee==_n_u_m_2]] ffdd Connect to a specific file descriptor. Available on IRIX systems. Field _n_u_m_1 is the decimal value of the file descriptor. Classes named ssttddiinn, ssttddoouutt, and ssttddeerrrr exist as alternate names for ffdd::00, ffdd::11, and ffdd::22. You can specify the numeric parameters with this alternate keyword syntax: ffdd[[..ffiillee__ddeessccrriippttoorr==_n_u_m_1]] gglloobbaall File global to all processes. Available on IRIX systems. This is a caching layer which distributes the cache across multiple SHMEM or MPI processes. Open and close operations are collective (require participation by all processes which access the file). All other operations are independently performed by one or more processes. The library allows multiple processes to concurrently access the file while maintaining coherency of buffered data. Specify one of the following options for _t_y_p_e: _t_y_p_e DDeessccrriippttiioonn pprriivvppooss Default. The file position is private to a process. All processes may seek to independent locations in the file. gglloobbppooss (Deferred). The file position is global to all processes. A seek or I/O operation by any process will affect the position for all processes. The numeric fields are as follows: _n_u_m_1 The size in 4096-byte blocks of each cache page. _n_u_m_2 Selects the number of cache pages to be used on each process. If there are _n processes, then _n * _n_u_m_2 cache pages are used. _n_u_m_2 buffer pages are allocated on every process which shares access to a global file. File pages are direct- mapped onto processes such that page _n of the file will always be cached on process (_n mmoodd NNPPEESS), where NNPPEESS is the total number of processes sharing access to the global file. Once the process is identified where caching of the file page will occur, a least-recently- used method is used to assign the file page to a cache page within the caching process. You can specify the numeric parameters with this alternate keyword syntax: gglloobbaall[[.._t_y_p_e]][[..ppaaggee__ssiizzee==_n_u_m_1]][[..nnuumm__ppaaggeess==_n_u_m_2]] iibbmm Record blocking for common record types on IBM operating systems. Deferred implementation on IRIX systems. Specify one of the following record formats for _t_y_p_e: _t_y_p_e FFoorrmmaatt ff Fixed-length record format. For _n_u_m_1, enter the logical record size in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes; if specified, _n_u_m_2 must be equal to _n_u_m_1. ffbb Fixed-length, blocked record format. For _n_u_m_1, enter the logical record size in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes; _n_u_m_2 must be an exact multiple of _n_u_m_1. uu Undefined record format. For _n_u_m_1, enter the maximum record size, in 8-bit bytes. vv Variable length record format. For _n_u_m_1, enter the maximum logical record size in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes. vvbb Variable length blocked record format. For _n_u_m_1, enter the maximum logical record size in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes. vvbbss Variable length blocked, spanned record format. For _n_u_m_1, enter the maximum logical record size in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes. No _s_u_b_t_y_p_e is accepted for the iibbmm class record formats. _n_u_m_1 does not need to be smaller than _n_u_m_2. You can specify the numeric parameters with this alternate keyword syntax: iibbmm[[.._t_y_p_e]][[..rreeccssiizzee==_n_u_m_1]][[..mmbbss==_n_u_m_2]] mmrr or ssddss Memory-resident and SDS-resident files. mmrr is a deferred implementation on IRIX systems. ssddss is not available on CRAY T3E systems or on IRIX systems. The mmrr and ssddss layers let you declare a byte-stream file, but the given file should reside in the specified medium as much as possible; this can improve performance. Enter one of the following for _t_y_p_e: _t_y_p_e LLooaadd SSppeecciiffiiccaattiioonn ssaavvee Default. Loads the file into the specified medium when the file is opened and writes the data back out when closed. ssccrr Scratch file. Does not attempt to load at open and discards data on close. Enter one of the following for _s_u_b_t_y_p_e: _s_u_b_t_y_p_e OOvveerrffllooww SSppeecciiffiiccaattiioonn oovvffll Default. Writes excess data that does not fit in the specified medium to the next lower layer. nnoovvffll If data does not fit in the specified medium, subsequent wwrriittee(1) operations fail. The mmrr and ssddss layers accept numeric fields. Generally, the numeric field specification represents best-efforts values. They are used for tuning purposes and usually do not cause errors if they are not satisfied precisely as specified. The fields are as follows: FFiieelldd VVaalluuee _n_u_m_1 Initial size of the memory or SDS allocation. Specified in 4096-byte blocks. Default is 0. _n_u_m_2 Maximum size of the memory or SDS allocation. Specified in 4096-byte blocks. Default is 46 s -1. _n_u_m_3 Increment size of the memory or SDS allocation. Specified in 4096-byte blocks. This value is used when allocating additional memory or SDS space. The default is 256 for SDS files and 32 for memory resident files. For example, if the SDS limit for a process is 1000 blocks, and ssddss..ssccrr::11550000 is specified, an initial SDS allocation of 1000 blocks is used. Similarly, if ssddss::550000::1100000000::11000000 was specified, the first request for SDS space would result in the allocation of 500 blocks. If possible, this is allocated contiguously, but it is not guaranteed. If a file size exceeds 500 blocks, an attempt is made to increase the file by an increment of 1000 blocks. If this attempt fails, whatever can be allocated is given to the file. Assuming no other SDS use, this is 500 blocks. At this point, the file assumes an overflow status. When using memory-resident files, you must ensure that not too much data is written to the file without limiting its size. Unrestrained and unmanaged growth of such a file can cause heap fragmentation and program abort. If this growth has used all available memory, the error message processor may be unable to issue a message. Therefore, such an abort may be difficult to diagnose and correct. It is recommended that the maximum memory size field be specified in all cases. (For example, mmrr..ssccrr::::1100000000 would limit such a file to approximately 5 Mwords of main memory.) You can specify the numeric parameters with this alternate keyword syntax: mmrr[[.._t_y_p_e[[.._s_u_b_t_y_p_e]]]][[..ssttaarrtt__ssiizzee==_n_u_m_1]] [[..mmaaxx__ssiizzee==_n_u_m_2]] [[..iinncc__ssiizzee==_n_u_m_3]] ssddss[[.._t_y_p_e[[.._s_u_b_t_y_p_e]]]][[..ssttaarrtt__ssiizzee==_n_u_m_1]] [[..mmaaxx__ssiizzee==_n_u_m_2]] [[..iinncc__ssiizzee==_n_u_m_3]] nnuullll Syntactic no-op. Available on IRIX systems. No optional fields are accepted. nnuullll may be specified where syntax demands a value, but no function is desired. This does not perform the same function as //ddeevv//nnuullll. nnoossvvee CDC NOS/VE record formats. Not available on IRIX systems. The following values are allowed for the _t_y_p_e and _n_u_m fields: _t_y_p_e VVaalluuee dd ANSI D format (variable-length) records. For _n_u_m_1, enter the maximum logical record size in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes. ff ANSI F fixed-length records. For _n_u_m_1, enter the logical record size in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes; _n_u_m_2 must be an exact multiple of _n_u_m_1. ss ANSI S format (segmented) records. For _n_u_m_1, enter the maximum logical record size. For _n_u_m_2, enter the maximum physical block size used in the lower-level layers. uu Undefined records. For _n_u_m_1, enter the maximum logical record size, in 8-bit bytes. For _n_u_m_2, enter the maximum physical block size in 8-bit bytes. vv NOS/VE V format records. The _n_u_m_1 field is not permitted. For _n_u_m_2, specify the size of the working buffer used in record blocking; if any logical records that are written exceed this size, a major performance penalty can result. You can specify the numeric parameters with this alternate keyword syntax (as noted previously, ..rreeccssiizzee may not be permitted for some _t_y_p_e_s): nnoossvvee[[.._t_y_p_e]][[..rreeccssiizzee==_n_u_m_1]][[..mmbbss==_n_u_m_2]] ssiittee Site layer. This option lets a site add custom I/O handlers for specific needs at load time. See the _A_p_p_l_i_c_a_t_i_o_n _P_r_o_g_r_a_m_m_e_r'_s _I/_O _G_u_i_d_e, for details. Available on IRIX systems. ssttddiinn, ssttddoouutt, or ssttddeerrrr Connects to specific file descriptors 0, 1, and 2, respectively. (See the ffdd class.) ssyysstteemm Generic system I/O layer. Selects bbmmxx, eerr9900, or ssyyssccaallll as appropriate. Available on IRIX systems. ssyyssccaallll System I/O call. Each I/O operation results in a corresponding system call. Available on IRIX systems. This layer does not accept any options on UNICOS or UNICOS/mk systems. On IRIX systems, it has one optional parameter as follows: ssyyssccaallll[[._c_b_o_p_t_i_o_n]] The _c_b_p_t_i_o_n can be one of the following values: aaiiooccbb The ssyyssccaallll layer is notified, via a signal, when the asynchronous I/O completes. nnooaaiiooccbb The ssyyssccaallll layer polls the completion status word to determine asynchronous I/O completion. This is the default value. ttaappee Tape I/O. Each logical record requested is a physical tape block. This is the same as bbmmxx. Deferred implementation on IRIX systems. For information about the ttmmff layer on IRIX systems, see the _I_R_I_X _T_M_F _U_s_e_r'_s _G_u_i_d_e, 007-3969-001. The _n_u_m_1 field represents the size of each buffer, in 4096-byte blocks. The _n_u_m_2 field represents the number of buffers. You can specify the numeric parameters with this alternate keyword syntax: ttaappee[[..bbuuffssiizzee==_n_u_m_1]][[..nnuumm__bbuuffffeerrss==_n_u_m_2]] tteexxtt Special character terminated records. Available on IRIX systems. Enter one of the following for _t_y_p_e: _t_y_p_e FFoorrmmaatt nnll Newline-separated records eeooff Newline-separated records and the special character sequence ~~ee on a line by itself delimiting EOF 220055 CYBER 205-style text file ccttssss CTSS-style text format This class accepts _n_u_m specifications. If specified, _n_u_m_1 represents the decimal value of the ASCII character to use to delimit records; the default varies depending on the _t_y_p_e. For _n_u_m_2, enter the requested working buffer size in bytes. You can specify the numeric parameters with this alternate keyword syntax: tteexxtt[[.._t_y_p_e]][[..nneewwlliinnee==_n_u_m_1]][[..bbuuffssiizzee==_n_u_m_2]] uusseerr User layer. This option allows a user to add custom I/O handlers for specific needs at load time. See the _A_p_p_l_i_c_a_t_i_o_n _P_r_o_g_r_a_m_m_e_r'_s _I/_O _G_u_i_d_e, for details. Available on IRIX systems. vvmmss Provides record blocking for common record types on VMS/MS operating systems. For _t_y_p_e, enter one of the following record formats: _t_y_p_e FFoorrmmaatt ff Fixed-length records vv Variable length records ss Segmented variable records Each _t_y_p_e accepts the following _s_u_b_t_y_p_es to specify the blocking format within the record type: _s_u_b_t_y_p_e FFoorrmmaatt ttaappee ANSI standard record format. This _s_u_b_t_y_p_e should be used with labeled VAX/VMS tapes. bbbb Binary blocked format. This _s_u_b_t_y_p_e should be used with files that are to be fetched or disposed with a BBBB or TTBB format, or with unlabeled magnetic tapes. This _s_u_b_t_y_p_e requires an enclosing blocking; for example, vvmmss..ss..bbbb,,bbmmxx or vvmmss..ss..bbbb,,ccooss. ttrr Transparent format. This _s_u_b_t_y_p_e should be used with files that are transferred between the VAX/VMS system by using ffeettcchh or ddiissppoossee (UNICOS/UNICOS/mk commands) and the TTRR format. Any other method that precisely transfers the disk image, including all VMS control words, will also work. Note that ffttpp does not correctly transfer nontext, variable-length record files. This class accepts _n_u_m_1 and _n_u_m_2 fields; they have a similar meaning to iibbmm class. For _t_y_p_e ss, _n_u_m_1 is ignored. For _t_y_p_e ff, _n_u_m_2 need not be a multiple of _n_u_m_1. You can specify the numeric parameters with this alternate keyword syntax: vvmmss[[.._t_y_p_e]][[.._s_u_b_t_y_p_e]][[..rreeccssiizzee==_n_u_m_1]][[..mmbbss==_n_u_m_2]] EEXXAAMMPPLLEESS The following are example FFIO specifications. Example 1: The following example specifies FORTRAN 77/UNICOS Fortran blocking with a working buffer of 128,000 bytes to allow efficient creation of logical records up to 127,992 bytes: f77::128000 Example 2: The following example specifies IBM VBS records with a block size of 16,384 bytes: ibm.vbs::16384 Example 3: The following example specifies a memory-resident layer with an initial memory size of 100 4096-byte blocks: mr:100 Example 4: The following example specifies VMS V records with a maximum record size of 1000 bytes: vms.v.tr:1000 Example 5: The following example specifies the SS-resident layer that loads from disk on open and saves to disk on close, does not allow overflow, has an initial size of 10 4096-byte blocks in SDS, grows to a maximum size of 559 blocks in minimum increments of 37 blocks: sds.save.novfl:10:559:37 See the _A_p_p_l_i_c_a_t_i_o_n _P_r_o_g_r_a_m_m_e_r'_s _I/_O _G_u_i_d_e, for more detailed information about FFIO specifications. NNOOTTEESS Some FFIO specification requirements are not obvious. For example, CYBER 205 R-type records must be requested with bbllxx..ccttssss,,tteexxtt..220055. The Fortran I/O library checks for conflicting attributes when file name and unit attributes are both present during OOPPEENN processing for a Fortran unit. The existence of an assign attribute for both the file and the unit results in an error condition. SSEEEE AALLSSOO _A_p_p_l_i_c_a_t_i_o_n _P_r_o_g_r_a_m_m_e_r'_s _I/_O _G_u_i_d_e aaccppttbbaadd(3F), aassssiiggnn(3F), ffffooppeenn(3C), ooppeennmmss(3F), ooppeennddrr (see ooppeennmmss(3F)), sskkiippbbaadd(3F) ddff(1), llnn(1), sseettff(1), ttppmmnntt(1), wwrriittee(1) aassggccmmdd(1), aassssiiggnn(1) iiaalllloocc(2), ooppeenn(2) SSDDSSAALLLLOOCC(3F) _A_p_p_l_i_c_a_t_i_o_n _P_r_o_g_r_a_m_m_e_r'_s _L_i_b_r_a_r_y _R_e_f_e_r_e_n_c_e _M_a_n_u_a_l for the printed version of this man page.