MODIFY-RESTART-CONTROL

This statement influences the duration of a restart.

Scope of validity

DBH administration

See also

DBH option RESTART-CONTROL on "RESTART-CONTROL"

Function

The MODIFY-RESTART-CONTROL administration statement allows you to modify the BUFFER-LIMIT and TALOG-LIMIT parameters specified using the DBH option RESTART-CONTROL.

You can use these parameters to reduce the duration of any restart by influencing the writing of afterimages to the database. It is possible to select different values for the buffers of the system access data and user data. Parameters not specified in the MODIFY-RESTART-CONTROL statement remain unchanged.

Low parameter values cause the afterimages to be written to the database frequently. This reduces the duration of physical repair in the event of a restart. However, if performance losses are incurred as a result of parameter values being selected that are too low and of an increased number of physical read and write accesses, you can use MODIFY-RESTART-CONTROL to adjust the parameter values during operation.

MODIFY-RESTART-CONTROL

RESTART-CONTROL = *BUFFER-LIMIT(...) / *TALOG-LIMIT(...)
	*BUFFER-LIMIT(...)
		|	SYSTEM-DATA-BUFFER = 50 / <integer 1..90>
		|	,USER-DATA-BUFFER = 50 / <integer 1..90>
	*TALOG-LIMIT(...)
		|	LIMIT = 128 / <integer 128..524288>

Operands

RESTART-CONTROL =

Specifies which value is to be changed.

RESTART-CONTROL = *BUFFER-LIMIT(...)
Controls the physical writing of the afterimages to the database.

SYSTEM-DATA-BUFFER = 50 / <integer 1..90>
Specifies a percentage limit for the writing of afterimages to the database for system access data. If the share of the total buffer space occupied by the buffers to be written exceeds the percentage specified for SYSTEM-DATA-BUFFER, afterimages are written to the database.

USER-DATA-BUFFER = 50 / <integer 1..90>
Specifies a percentage limit for the writing of afterimages to the database for user data. If the share of the total buffer space occupied by the buffers to be written exceeds the percentage specified for USER-DATA-BUFFER, afterimages are written to the database.

RESTART-CONTROL = *TALOG-LIMIT(...)
Specifies the limit for how much of the TA-LOG file can be occupied by afterimages. As of this limit, afterimage blocks are written to the database.

LIMIT = 512 / <integer 128..524288>
Specifies the new limit value in units of 4 Kbytes.

Administration command in ISP format and at the CALL DML interface

Three administration commands with the format OPT,RESTART, each with specific operands, correspond to the MODIFY-RESTART-CONTROL administration statement here.

OPT,RESTART,B[UFFER-LIMIT],U[SER-DATA-BUFFER]=n[,S[YSTEM-DATA-BUFFER]=m]
OPT,RESTART,B[UFFER-LIMIT],S[YSTEM-DATA-BUFFER]=n[,U[SER-DATA-BUFFER]=m]
OPT,RESTART,T[ALOG-LIMIT]=l

Percentage values expressed as integers between 1 and 90 can be specified for n and m.

An integer between 128 and 524288 can be specified for l.