Defining the primary CF lock structure

Requirements: To use VSAM RLS, you must define a single, master CF lock structure. If, however, you use the DUPLEX attribute, you only define one CF lock structure. That is because the structure gets created automatically into the secondary CF.

For maximum availability, define nonvolatile lock structures. CF lock structures enforce the protocol restrictions for VSAM RLS data sets and maintain the record-level locks and other DFSMSdfp serialization. Ensure that the CF lock structures have universal connectivity, so that they are accessible from all systems in the Parallel Sysplex® that support VSAM RLS. For system-managed duplexing, define the lock structure as duplexed (DUPLEX (ENABLED) or DUPLEX (ALLOWED) in the CFRM policy.

For more information about system-managed lock structure duplexing, see Recovering the CF lock structure.

The Primary CF lock structure is named IGWLOCK00. Use the XCF coupling definition process to define it. To estimate its size requirements in megabytes, use the following formula (a megabyte is 1048576 bytes in this case):

10M * number_of_systems * lock_entry_size

where:

number_of_systems

Is the number of systems in the Parallel Sysplex

lock_entry_size

Is the size of each lock entry. This value depends on the MAXSYSTEM value that is specified to the IXCL1DSU Couple Data Set format utility.

Use the following table to determine the actual lock entry size for the different MAXSYSTEM setting values:

Table 1. Effect of MAXSYSTEM Value on Lock Table Entry Size
MAXSYSTEM Value	Lock Entry Size
7 or less	2 bytes
>= 8 and < 24	4 bytes
>= 24 and <= 32	8 bytes

Table 2 shows some sample lock allocation estimates:

Table 2. CF Lock Structure Sizing Examples
MAXSYSTEM Value	Number of systems	Total Lock Size
<= 7	2	64MB
<= 7	4	80MB
<= 23	8	320 MB
<default> =8	2	80 MB
	4	160 MB
	8	320 MB
32	2	160 MB
	4	320 MB
	8	320 MB

These lock size estimates include the memory requirements for both the lock table and the record-lock memory. Use these estimates as rough initial values to help you attain a locking structure with a desired false contention target of approximately one-half of 1% or less. Contact your marketing representative for help in arriving at an initial estimate that more closely matches your specific configuration.

Note: XES rounds up the number of lock entries to the next highest power of two. For example, if you base your calculations on 2 * 10M = 20M locks, XES allocates the structure with 32M locks.

The primary DFSMS CF lock structure, IGWLOCK00, has persistent connections and is a persistent structure. To delete this structure you must use the operator command:

V SMS,SMSVSAM,FORCEDELETELOCKSTRUCTURE