Data set attributes play a significant role in FTP performance.
If your environment permits, tune both BLOCKSIZE and LRECL according
to the following recommendations:
- Use half a track as the block size.
- For IBM® 3380 DASD, use 23424
as the block size with an LRECL of 64 bytes.
- For IBM 3390 DASD or IBM9334,
use 27968 as the block size with an LRECL of 64 bytes.
- Use FB as the data set allocation format.
- Use cached DASD controllers.
- If your environment permits, use a preallocated data set for FTP
transfers into MVS™.
The following configuration data statements apply to FTP server's
allocation of data sets.
- AUTOMOUNT
- AUTORECALL
- BLKSIZE
- BUFNO
- CONDDISP
- DATACLASS
- DCBDSN
- DIRECTORY
- DSNTYPE
- EATTR
- LRECL
- MGMTCLASS
- MIGRATEVOL
- PDSTYPE
- PRIMARY
- RECFM
- RETPD
- SECONDARY
- SPACETYPE
- STORCLASS
- UCOUNT
- UMASK
- UNITNAME
- VCOUNT
- VOLUME
See z/OS Communications Server: IP Configuration
Reference for more detailed information about these
keywords.
Some of these allocation variables might provide duplicate information.
FTP passes all variables that are specified to the z/OS® dynamic allocation function to determine
which of the specifications take precedence, except for the following
exceptions:
- If the data set organization is physical sequential, directory
blocks are not sent.
- If neither primary nor secondary space quantities are specified,
the allocation units value is not sent.
For example, the model DCB (DCBDSN) might have a record format
(RECFM) that differs from the record format specified by a data class
and from the one explicitly specified by the client. The order of
precedence for dynamic allocation variables are as follows:
- Any FTP.DATA statements or SITE parameters explicitly specified
or in effect by default.
- Any attributes picked up from the model DCB and not otherwise
explicitly specified.
- Any attributes picked up from the data class and not previously
derived from 1 and 2 above.
- Any system allocation defaults.