Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1998-10-29
2001-12-18
Iqbal, Nadeem (Department: 2184)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C711S161000
Reexamination Certificate
active
06332199
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application contains subject matter which is related to the subject matter of the following applications, each of which is assigned to the same assignee as this application and filed on the same day as this application. Each of the below listed applications is hereby incorporated herein by reference in its entirety:
“A METHOD OF PERFORMING CHECKPOINT/RESTART OF A PARALLEL PROGRAM,” by Meth, et al., Ser. No. 09/181,985, and
“A SYSTEM OF PERFORMING CHECKPOINT/RESTART OF A PARALLEL PROGRAM,” by Meth et al., Ser. No. 09/181,981,
“PROGRAM PRODUCTS FOR PERFORMING CHECKPOINT/ RESTART OF A PARALLEL PROGRAM,” by Meth et al., Ser. No. 09/182,555,
“CAPTURING AND IDENTIFYING A COMPLETE AND CONSISTENT SET OF CHECKPOINT FILES,” by Meth et al., Ser. No. 09/182,175,
“RESTORING CHECKPOINTED PROCESSES WITHOUT RESTORING ATTRIBUTES OF EXTERNAL DATA REFERENCED BY THE PROCESSES,” by Meth et al., Ser. No. 09/182,725, now U.S. Pat. No. 6,256,751.
TECHNICAL FIELD
This invention relates, in general, to restoring checkpointed processes and, in particular, to adjusting values of selected information, such as environment variables, after using checkpointed data to restore a process.
BACKGROUND ART
A requirement of any robust computing environment is to be able to recover from errors, such as device hardware errors (e.g., mechanical or electrical errors) or recording media errors. In order to recover from some device or media errors, it is necessary to restart a process, either from the beginning or from some other point within the process.
To facilitate recovery of a process, especially a long running process, intermediate results of the process are taken at particular intervals. This is referred to as checkpointing the process. Checkpointing enables the process to be restarted from the last checkpoint, rather than from the beginning of the process.
When a process is restarted, it is restored to the state it was in when the checkpoint was taken. Thus, any and all changes subsequent to the last checkpoint are undone. This includes any changes that have been made to the environment variables associated with the process. Once the process is restored to its former state, it continues to execute from that point.
Based on the foregoing, a need exists for a restore capability that does not require that all information be restored to the point at which the checkpoint was taken. That is, a need exists for a capability that allows selected information to remain unrestored. A need exists for a capability that enables selected information to be adjusted as part of the restoration, such that the selected information reflects the current operating environment rather than the operating environment at the time the checkpoint was taken.
SUMMARY OF THE INVENTION
The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a method of restoring checkpointed processes. The method includes, for instance, restarting a process on a computing unit from a checkpoint taken of the process; restoring one or more information components of the process using data obtained from the checkpoint; changing a value of a restored information component to a new value; and executing the process using the new value of the one restored information component.
In one example, the one or more information components include one or more environment variables. Further, in another example, the new value is saved, prior to restoring the one or more environment variables. For instance, the new value is saved in a stack of the process.
In another embodiment, the one or more environment variables are located in a stack and/or a data section of the process, and the method includes restoring the data section using data obtained from the checkpoint, wherein the restoring of the data section includes restoring any of the one or more environment variables located within the data section. The method further includes copying the new value from the stack to the restored data section, and restoring the stack using data obtained from the checkpoint. The restoring of the stack includes restoring any of the one or more environment variables located within the stack. Further, the changing of the value includes replacing the value of the restored environment variable located in either the restored stack or the restored data section with the new value, which is located in the restored data section.
In another aspect of the present invention, a method of restoring checkpointed processes is provided. The method includes, for instance, restarting a process on a computing unit from a checkpoint taken of the process. The process includes one or more environment variables located in a stack of the process and/or a data section of the process. The method further includes saving in the stack at least one new value for at least one environment variable; restoring the data section using information obtained from the checkpoint; copying the at least one new value from the stack to the restored data section; restoring the stack, subsequent to the copying, using information obtained from the checkpoint; and replacing at least one value for the at least one environment variable located in the restored stack and/or the restored data section with the at least one new value saved in the stack.
In a further aspect of the present invention, a system of restoring checkpointed processes is provided. The system includes, for instance, means for restarting a process on a computing unit from a checkpoint taken of the process; means for restoring one or more information components of the process using data obtained from the checkpoint; means for changing a value of one restored information component to a new value; and means for executing the process using the new value of the restored information component.
In yet a further aspect of the present invention, a system of restoring checkpointed processes is provided. The system includes, for example, a computing unit adapted to restart a process from a checkpoint taken of the process, and to restore one or more information components of the process using the data obtained from the checkpoint. The computing unit is further adapted to change a value of one restored information component to a new value, and to execute the process using the new value.
In another aspect of the present invention, a system of restoring checkpointed processes is provided. This system includes, for example, means for restarting a process on a computing unit from a checkpoint taken of the process, wherein the process includes one or more environment variables located in at least one of a stack of the process and a data section of the process; means for saving in the stack at least one new value for at least one environment variable; means for restoring the data section using information obtained from the checkpoint; means for copying the at least one new value from the stack to the restored data section; means for restoring the stack, subsequent to the copying, using information obtained from the checkpoint; and means for replacing at least one value for the at least one environment variable located in at least one of the restored stack and the restored data section with the at least one new value saved in the stack.
In yet another aspect of the present invention, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine to perform a method of restoring checkpointed processes is provided. The method includes, for instance, restarting a process on a computing unit from a checkpoint taken of the process; restoring one or more information components of the process using data obtained from the checkpoint; changing a value of one restored information component to a new value; and executing the process using the new value of the restored information component.
In another aspect of the present invention, an article of manufacture, including at least one computer usable medium having computer readable progra
Agbaria Adnan M.
Meth Kalman Zvi
Cutter, Esq. Lawrence D.
Gonzalez, Esq. Floyd A.
Heslin Rothenberg Farley & & Mesiti P.C.
International Business Machines - Corporation
Iqbal Nadeem
LandOfFree
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