HP 3000 Manuals HP 3000 Manuals
3000/XL Network Services Enhancements by Lorraine Bartlett--Information Networks Division NFT CHECKPOINT/RESTART ENHANCEMENT The Network File Transfer (NFT) service of the 3000/XL Network Services (NS) enhancement includes a Checkpoint/Restart facility. Using the Checkpoint/Restart facility allows users of the NFT service to resume file transfers that have prematurely aborted due to some transient problem, such as a link failure. To invoke the Checkpoint/Restart facility, the user specifies a new keyword, CHECKPT, in the NFT command line. The "Restart ID", a number that uniquely identifies the transfer, is returned to the user before the file transfer begins. The actual file transfer occurs normally. A "handshake sequence" occurs between the source and target HP 3000 systems at periodic intervals (optionally specified by the user) in order to restart a file transfer in case it is prematurely aborted. Using this Checkpoint/Restart facility, it is possible to restart the transfer from the point where the last handshake sequence occurred. For example, if the transfer is 44% complete at the last handshake sequence recorded prior to a link failure, the transfer can be later restarted with 44% of the transfer already completed. To restart a transfer that previously aborted, specify a new keyword, RESTART, in the NFT command line along with the same Restart ID that was returned when CHECKPT was specified. NFT then attempts to restart the transfer from the point where the last handshake sequence occurred. The restarted transfer continues to make periodic handshake sequences, in the event of another failure from where another restart may be done. The Checkpoint/Restart facility is supported on HP 3000/V systems (NS/V Services version A.00.05 and later) and HP 3000/XL systems (NS/XL Services version B.00.05, available with this release) with the Network Services installed. All features of 3000 NS NFT are supported when used in conjunction with the Checkpoint/Restart facility. All MPE V/E file types are supported, except message files and circular files. RFA COMPRESSION ENHANCEMENT The Remote File Access (RFA) service of the 3000/XL Network Services (NS) enhancement includes data compression. RFA data compression provides faster data transfer, especially over a slow link and when the file being remotely accessed has large records with repeated characters. To invoke data compression for the RFA service, specify the keyword, COMP, in the :DSLINE command. Prior to this release, specifying COMP on the :DSLINE command only compressed Network File Transfer (NFT) data. Now, with this RFA compression enhancement, the COMP keyword also compresses any RFA data associated to the remote environment specified in the :DSLINE command. For example, issuing the command :DSLINE NODE1;COMP allows for compression of all RFA and NFT data to the remote node NODE1. To terminate data compression to the specified environment, the user specifies the keyword, NOCOMP, in the :DSLINE command. Issuing this command prevents data compression of any new remote files opened and prevents data compression of any future NFT data to the environment specified in the :DSLINE command. Files opened remotely while compression is in effect for the environment remain in compressed mode even after the :DSLINE;NOCOMP command is issued. The algorithm for RFA data compression is the same as the algorithm used with NS NFT compression and also with DS Services compression. Each sequence of up to 64 consecutive repeated characters is compressed to bytes and repeated blanks are compressed to bytes. Without RFA compression enabled, the RFA service can transfer up to 29,900 bytes of data at one time. However, due to overhead associated with managing a compressed data transfer, the RFA service with compression enabled can transfer up to a maximum of 29,000 bytes of data at one time. RFA compression only compresses data transmitted with the FREAD, FREADDIR, FREADBACKWARD, FWRITE, FWRITEDIR and FUDPATE intrinsics. Therefore, RFA compression is not supported with the Remote DataBase Access (RDBA) service. RFA compression is currently only available on HP 3000/XL systems with version B.00.05 of the 3000/XL Network Services. (RFA compression is planned for version A.00.12 of the 3000/V Network Services.) If the user requests RFA compression of a file residing on a system that does not support RFA compression (such as an HP 3000/V system), RFA completes the request without compressing the RFA data. No error or warning messages are issued in this situation. All file types (accessed using the above list of file intrinsics) can be compressed except those remote files accessed with no-wait IO.