You are looking for some example JCL to perform a LIBR multifile backup
// JOB XXXLIBR Multifile BACKUP
// MTC REW,181
// TLBL SARTAPE,'SARBACK.001,H'
// EXEC LIBR
BACKUP L=SARLIB TAPE=SYS010 TAPEL=SARTAPE RESTORE=ONLINE
/*
// TLBL SARTAPE,'SARBACK.002,H'
// EXEC LIBR
BACKUP L=SARXLIB TAPE=SYS010 TAPEL=SARTAPE RESTORE=ONLINE
/*
// MTC REW,SYS010
/&