Defining VSAM string settings for LSR (STRINGS)

STRINGS is used to determine the number of strings and thereby the number of concurrent operations possible against the LSR pool (assuming that there are buffers available).

Effects

The STRINGS parameter relating to files using LSR has the following effects:

Where useful

The STRINGS parameter can be used in CICS systems with VSAM data sets.

Limitations

A maximum of 255 strings is allowed per pool.

Recommendations

See Number of strings considerations for ESDS files and VSAM tuning: general objectives.

How implemented

The number of strings is defined by the STRNO parameter in the file definition on the CSD, which limits the concurrent activity for that particular file.

How monitored

The effects of the STRINGS parameter can be seen in increased response times for each file entry. The CICS LSRPOOL statistics give information on the number of data set accesses and the highest number of requests for a string.

Examination of the string numbers in the CICS statistics shows that there is a two-level check on string numbers available: one at the data set level (see File control statistics), and one at the shared resource pool level (see LSRpool statistics).

RMF™ can show I/O contention in the DASD subsystem.

Related tasks
VSAM and file control: improving performance
VSAM tuning: general objectives
Defining VSAM buffer allocations for NSR (INDEXBUFFERS and DATABUFFERS)
Defining VSAM buffer allocations for LSR
Defining VSAM string settings for NSR (STRINGS)
Specifying maximum keylength for LSR (KEYLENGTH and MAXKEYLENGTH)
Specifying resource percentile for LSR (SHARELIMIT)
Using VSAM local shared resources (LSR)
Using Hiperspace buffers
Permitting VSAM subtasking (SUBTSKS=1)
Using data tables to improve performance
Using coupling facility data tables to gain performance benefits
Performance aspects of VSAM record-level sharing (RLS)
[[ Contents Previous Page | Next Page Index ]]