When PDSMAN is active, it front ends the initialization of ISPF logical sessions. When $EZYEDIT CMDTABUPDT=Y is specified (or allowed to default), PDSMAN inserts certain of his commands into the ISPF command table. These commands are defined on $EZYCMD control statements.
Here is the default rule for the SPACE command as described in the PDSMAN Administrator Guide r7.7:
$EZYCMD COMMAND=SPACE ACT=SELECT PGM(PDSEASY) PARM(SPACE...&ZPARM.) NEWAPPL(PDSM) ACT=SCRNAME(SPACE) TRUNC=2 DESC=EZYEDIT Space Display
The TRUNC parameter of the rule indicates the minimum number of characters that must be entered to find a match with the command. If this value is set to zero or allowed to default, the complete command must be entered.