disk i/o structures

disk i/o structures specifies the initial number of disk I/O control blocks SAP ASE allocates at start-up.

Summary Information

Default value


Range of values




Display level


Required role

System administrator

Configuration group

Disk I/O, Memory Use

User processes require a disk I/O control block before SAP ASE can initiate an I/O request for the process. The memory for disk I/O control blocks is preallocated when SAP ASE starts. To minimize the chance of running out of disk I/O structures, you should configure disk i/o structures to as high a value as your operating system allows. See your operating system documentation for information on concurrent disk I/Os.

Use sp_sysmon to determine whether to allocate more disk I/O structures. See Performance and Tuning Series: Monitoring SAP Adaptive Server with sp_sysmon. You can set the max async i/os per server configuration parameter to the same value as disk i/o structures.