Dynamic access method switching for open data sets

Abstract

A method for switching between access methods while a data set is open includes attempting, on behalf of a first system, to gain access to a control interval of a data set. The method further determines whether the data set is already open by a second system. In the event the data set is already open, the method uses a first access method to access the control interval. In the event the data set is not already open, the method uses a second access method to access the control interval. In certain embodiments, the first access method is an RLS (Record Level Sharing) access method and the second access method is a base VSAM (Virtual Storage Access Method) access method. A corresponding system and computer program product are also disclosed.

1 . A method for switching between access methods while a data set is open, the method comprising:
 attempting, on behalf of a first system, to gain access to a control interval of a data set;   determining whether the data set is already open by a second system;   in the event the data set is already open, using a first access method to access the control interval; and   in the event the data set is not already open, using a second access method to access the control interval.   
     
     
         2 . The method of  claim 1 , wherein the first access method is an RLS (Record Level Sharing) access method. 
     
     
         3 . The method of  claim 1 , wherein the second access method is a base VSAM (Virtual Storage Access Method) access method. 
     
     
         4 . The method of  claim 1 , wherein the data set is a VSAM data set. 
     
     
         5 . The method of  claim 4 , wherein the VSAM data set is a non-recoverable VSAM data set. 
     
     
         6 . The method of  claim 1 , in the event the data set is not already open but the control interval was previously accessed using the first access method, using the first access method to access the control interval. 
     
     
         7 . The method of  claim 1 , wherein using the first access method comprises using the first access method only if the data set is marked as eligible to use the first access method. 
     
     
         8 . A computer program product for switching between access methods while a data set is open, the computer program product comprising a computer-readable medium having computer-usable program code embodied therein, the computer-usable program code comprising:
 computer-usable program code to attempt, on behalf of a first system, to gain access to a control interval of a data set;   computer-usable program code to determine whether the data set is already open by a second system;   computer-usable program code to, in the event the data set is already open, use a first access method to access the control interval; and   computer-usable program code to, in the event the data set is not already open, use a second access method to access the control interval.   
     
     
         9 . The computer program product of  claim 8 , wherein the first access method is an RLS (Record Level Sharing) access method. 
     
     
         10 . The computer program product of  claim 8 , wherein the second access method is a base VSAM (Virtual Storage Access Method) access method. 
     
     
         11 . The computer program product of  claim 8 , wherein the data set is a VSAM data set. 
     
     
         12 . The computer program product of  claim 11 , wherein the VSAM data set is a non-recoverable VSAM data set. 
     
     
         13 . The computer program product of  claim 8 , further comprising computer-usable program code to, in the event the data set is not already open but the control interval was previously accessed using the first access method, use the first access method to access the control interval. 
     
     
         14 . The computer program product of  claim 8 , wherein using the first access method comprises using the first access method only if the data set is marked as eligible to use the first access method. 
     
     
         15 . A system for switching between access methods while a data set is open, the system comprising:
 at least one processor;   at least one memory device operably coupled to the at least one processor and storing instructions for execution on the at least one processor, the instructions causing the at least one processor to:
 attempt, on behalf of a first system, to gain access to a control interval of a data set; 
 determine whether the data set is already open by a second system; 
 in the event the data set is already open, use a first access method to access the control interval; and 
 in the event the data set is not already open, use a second access method to access the control interval. 
   
     
     
         16 . The system of  claim 15 , wherein the first access method is an RLS (Record Level Sharing) access method. 
     
     
         17 . The system of  claim 15 , wherein the second access method is a base VSAM (Virtual Storage Access Method) access method. 
     
     
         18 . The system of  claim 15 , wherein the data set is a non-recoverable VSAM data set. 
     
     
         19 . The system of  claim 15 , wherein the instructions further cause the at least one processor to, in the event the data set is not already open but the control interval was previously accessed using the first access method, use the first access method to access the control interval. 
     
     
         20 . The system of  claim 15 , wherein using the first access method comprises using the first access method only if the data set is marked as eligible to use the first access method.