STRINGS is used to determine the number of concurrent operations possible against the file and against the VSAM base cluster to which the file relates.
The STRINGS parameter for files using NSR has the following effects:
Strings represent a significant part of the virtual storage requirement of most CICS® systems. With CICS, this storage is above the 16MB line.
The STRINGS parameter should be used in CICS systems that use VSAM NSR files in CICS file control.
A maximum of 255 strings can be used as the STRNO or BSTRNO in the ACB.
See Number of strings considerations for ESDS files and VSAM tuning: general objectives.
The number of strings is defined by the STRINGS parameter in the CICS file definition on the CSD. It corresponds to the VSAM parameter in the ACB except where a base file is opened as the first for a VSAM data set; in this case, the CICS-accumulated BSTRNO value is used as the STRNO for the ACB.
The effects of the STRINGS parameter can be seen in increased response times and monitored by the string queueing statistics for each file definition. RMF™ can show I/O contention in the DASD subsystem.