1) try to comfigure then syslog , with this all info will be copied to system syslog , but in heavy traffic environmnet, ddos protection and other limitation will prevent from logging too much messages
2) better options will use jflow/netflow and send packet statistics to external server
first 100 bytes of each IP PACKET , for extended period of time say 1 hr.
Leaving aside the fact that SRX is not able to syslog payload beyond L4 header, let's do some simple math, shall we? Let's say this is SRX100 with 100Mbps of 512-Byte packets. That's 24Kpps.
So, for 1 hour (3600 secs) it will generate 69GBytes of logging. Then You'd need:
1/ since ANY SRX won't be able to store it locally, You need an external syslog server capable of writing 24Kpps of syslog messages per SRX
2/ this syslog server must have an appropriately sized disk
1/ You need to look elsewhere/beyond SRX logging capabilities to meet Your requirement
2/ if You still wnat to pursue that with SRX, configure packet replication on SRX itself (by means of anaylzer/port-mirroring or simply have a VLAN with mac-learning disabled) and funnel the replicated packets to a Linux server of Your choice with Wireshark running on it. Of course, don't forget the server disk requirements.