VSAM LSR Pool Statistics

The VSAM LSR (Local Shared Resources) Pool Statistics report shows information about buffer pools and is organized by LSR Pool.

Each entry line of the report represents a subpool. The components of a VSAM cluster will use the buffer subpool with buffers of at least the same CI size as those of the VSAM components.

Because of the complexity of managing VSAM access, you should discuss the results of your measurements and possible changes with your site's VSAM performance specialist.

Report details

Pool shows the identification number of the pool.

Strings contains the number of placeholders defined for the pool. A string is a request to a VSAM data set requiring positioning within the data set. For each concurrent file operation, VSAM requires one or more strings.
Key length shows the maximum key length for data sets in the pool. If none of the data sets is keyed, the report displays a "0".

Click next to a Pool to view additional detail about it:

Subpool type identifies the resource pool. INDEX: an index component resource pool; DATA: a data component resource pool; ANY: both data and index component may use this resource pool.

Click next to a Subpool type to view additional detail about the data set assigned to it:

DDNAME is the DDNAME from the Data Set Characteristics report. It is the data definition name assigned to the data set. [MORE] Click to view the Data Set Characteristics report, which shows the characteristics of all data sets accessed for the measured job step during the measurement session.
Access method shows the access method to process the data set as well as the VSAM component. [MORE]
Data set name shows the name of the data set assigned to the subpool.
Buffer length shows the size of the virtual and hiperspace buffers in the subpool.
Buffers:
BUFNO: the number of non-hiperspace buffers in the subpool.
Reads - with I/O shows the number of I/Os that occurred to bring data into the pool.
Reads - Without I/O shows the number of retrievals during which the requested data was found in the subpool (also known as lookasides).
Hit rate shows the number of reads without I/O divided by the sum of the number of reads with I/O plus the number of reads without I/O, multiplied by 100.
Writes - User shows the number of writes that the user initiated.
Writes - Non-user shows the number of writes that occurred because no buffer was available. The program did not initiate these writes.
Hiperspace buffers:

HBUFNO: the number of hiperspace buffers in the subpool.
Reads - Success: the number of times a hiperspace buffer was successfully read from the LSR hiperspace buffer pool to a local LSR buffer pool.
Reads - Fail: the number of times a hiperspace buffer was reclaimed and could not be read from the LSR hiperspace buffer pool to a local LSR buffer pool.
Writes - Success: the number of times a hiperspace buffer was successfully written from a local LSR buffer pool to a hiperspace buffer pool.
Writes - Failed: the number of time a hiperspace buffer was reclaimed and could not be written to a hiperspace buffer pool.

Note: Hiperspace buffering helps to reduce DASD I/O by using expanded storage for LSR buffers. Hiperspace storage is not byte addressable. Therefore, to reference data stored in hiperspace, an application must first move each 4K page to a non-hiperspace LSR buffer pool. The reporting of hiperspace statistics represents movement of buffers to and from hiperspace buffer pools.

More about the Data Set Characteristics report