International Business Machines Corporation

Teresa A Meriwether

Bhaskar Sinha

Balakrishna Raghavendra Iyer

Ian Beaumont Shields

Elton B Sherwin, Jr

Barron Cornelius Housel, Iii

Peter Williams Volkmar

Method, appartus and program products for persistent cache synchronization for communications over an external communication link between a client protocol conversion application executing on a first computer and a server protocol conversion application executing on a second computer located remote from the first computer are provided. Protocol conversion applications are provided on both the host side and the terminal side of the external communication link to provide communications over the external communication link using a differenced communication data stream which includes a reduced volume of data for transmittal. A checkpoint is provided to allow for improved performance on start up of a new communication session over the external communication link between the client application and the server application by initiating a checkpoint request and transmitting the request from the client to the server. The active protocol cache of the server is copied to a checkpoint cache responsive to a received checkpoint request. A checkpoint confirmation message is sent to the client from the server. Responsive to receipt of a checkpoint confirmation message indicating successful copying of the server active protocol cache to a checkpoint cache, the client application creates a checkpoint cache of the first computer as a copy of the protocol cache of the first computer. The first computer creates a checkpoint cache by first creating a temporary cache before initiating the checkpoint and on receipt of a confirmation from the server, converting the temporary cache to a confirmed checkpoint cache.

Persistent cache synchronization and start up system

A session is established between a terminal and host, each of which are operative to communicate according to a communications protocol. A communications channel is established between the terminal and the host via a client and a server of a communications network, the client being connected to the terminal and the server being connected to the host. Terminal type information is communicated from the client to the server via the communications channel. An indication of readiness to communicate data between the terminal and the host is communicated between the server and the client via the communications channel. Messages are communicated between the client and the terminal and between the server and the host according to the communications protocol to emulate communication of session establishment messages operative to establish a session between the terminal and the host according to the communications protocol without requiring communication of the session establishment messages via the communications channel. Related apparatus and computer program products are also discussed.

Methods, system and computer program products for establishing a session

Describes novel methods for compressing data character strings into 'storage optimized indices' (SOIs) and stores their adaptive Ziv Lempel (AZL) indices, called 'evolution based indices' (EBIs), in fields in corresponding entries in a SOI dictionary. The method also compresses data using the SOI dictionary, which accesses the corresponding EBIs for representing the compressed data. The EBIs are put into storage, or transmitted to a receiving location. Greater data compression processing efficiency is obtained by using the SOI dictionary than is available using prior types of AZL dictionaries. The disclosure further describes methods for decompressing EBI indices into corresponding phrases at a receiving location using either a conventional AZL dictionary or a SOI dictionary after translating received EBIs into SOIs. Also described is a submethod for phrase length determination for use in the decompression process. Using this phrase length detection, received phrases are decompressed in their reverse character order through a buffer, or directly in a target storage area, or in a combination of the latter two techniques. The phrase length may be stored in corresponding dictionary entries to avoid a length tracing process in the invention.

Transmission compatibility using custom compression method and hardware

Improvements are made to standard run length encoding compression techniques to permit frequently occurring repeated bytes to be dynamically redefined or reset to a default value such as a blank character, repeated multiple byte units or strings to be more efficiently coded and run length encoded enhancements allow compression of data where characters are represented by multiple bytes. The Sequence Control Byte (SCB) is modified to communicate indications to a receiver that the compression mode of 1 to N bytes per character is being changed and to indicate what the change is or that a con, non master repeat character frequently encountered in data is being redefined to be another character or that characters are going to be encoded in multiple bytes. The SCB format which is well known in the prior art is modified to include specific bit patterns or codes in the first two bits of the SCB byte to indicate setting of the bytes per character encoding mode to a different value, resetting the encoding mode to a default value or redefining a commonly repeated character or defining a character to be multiple bytes or a string of characters which may be multiple byte characters. The other six bits of the SCB are assigned code values unused in the prior art to indicate the number of tines that a defined character is to be repeated, whether a master character that has been defined is to be repeated or whether a character string is to be repeated. Two fields of data are thus formatted in the SCB with new values to indicate to a receiver these new criteria.

Multimode and multiple character string run length encoding method and

A method of transmitting compressed data using a Ziv-Lempel compression/expansion algorithm, using an adaptive Ziv-Lempel (AZL) dictionary modified to a mature state. The mature state is signaled by a time to freeze signal sent as a switch-over signal from a transmitting location to each receiving location. These signals freeze and synchronize the AZL dictionaries at both locations, and starts a translation of the frozen AZL dictionary to a static SZL dictionary--at least at the transmitting location. The SZL dictionary is then used to compress records being transmitted. An index translation process is generates translation information to allow the receiving locations to decompress SZL indices into original characters. The AZL-to-SZL dictionary translation process re-organizes the frozen AZL to an SZL dictionary. The SZL process is used until either the end of the inputted sequence, or a time to unfreeze signal is generated. An SZL to AZL switch-over signal is generated in response to the time to unfreeze signal, which in turn signals a switch over back to the AZL process and invokes the saved frozen AZL dictionary to be used to until mature to on the current input data stream at which time the AZL is frozen and a switch-over signal is provided and a new SZL is generated.

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Cary, NC, United States of America

Teresa A Meriwether